diff --git a/Database/Monarch/Binary.hs b/Database/Monarch/Binary.hs
--- a/Database/Monarch/Binary.hs
+++ b/Database/Monarch/Binary.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE FlexibleContexts #-}
 -- | TokyoTyrant Original Binary Protocol(<http://fallabs.com/tokyotyrant/spex.html#protocol>).
 module Database.Monarch.Binary
     (
@@ -22,6 +23,7 @@
 import Data.ByteString hiding (length, copy)
 import Control.Applicative
 import Control.Monad.Error
+import Control.Monad.Trans.Control
 
 import Database.Monarch.Raw
 import Database.Monarch.Utils
@@ -29,9 +31,10 @@
 -- | Store a record.
 --   If a record with the same key exists in the database,
 --   it is overwritten.
-put :: ByteString -- ^ key
+put :: (MonadBaseControl IO m, MonadIO m) =>
+       ByteString -- ^ key
     -> ByteString -- ^ value
-    -> Monarch ()
+    -> MonarchT m ()
 put key value = communicate request response
     where
       request = do
@@ -46,9 +49,10 @@
 -- | Store a new record.
 --   If a record with the same key exists in the database,
 --   this function has no effect.
-putKeep :: ByteString -- ^ key
+putKeep :: (MonadBaseControl IO m, MonadIO m) =>
+           ByteString -- ^ key
         -> ByteString -- ^ value
-        -> Monarch ()
+        -> MonarchT m ()
 putKeep key value = communicate request response
     where
       request = do
@@ -63,9 +67,10 @@
 
 -- | Concatenate a value at the end of the existing record.
 --   If there is no corresponding record, a new record is created.
-putCat :: ByteString -- ^ key
+putCat :: (MonadBaseControl IO m, MonadIO m) =>
+          ByteString -- ^ key
        -> ByteString -- ^ value
-       -> Monarch ()
+       -> MonarchT m ()
 putCat key value = communicate request response
     where
       request = do
@@ -79,10 +84,11 @@
 
 -- | Concatenate a value at the end of the existing record and shift it to the left.
 --   If there is no corresponding record, a new record is created.
-putShiftLeft :: ByteString -- ^ key
+putShiftLeft :: (MonadBaseControl IO m, MonadIO m) =>
+                ByteString -- ^ key
              -> ByteString -- ^ value
              -> Int  -- ^ width
-             -> Monarch ()
+             -> MonarchT m ()
 putShiftLeft key value width = communicate request response
     where
       request = do
@@ -97,9 +103,10 @@
 
 -- | Store a record without response.
 --   If a record with the same key exists in the database, it is overwritten.
-putNoResponse :: ByteString -- ^ key
+putNoResponse :: (MonadBaseControl IO m, MonadIO m) =>
+                 ByteString -- ^ key
               -> ByteString -- ^ value
-              -> Monarch ()
+              -> MonarchT m ()
 putNoResponse key value = yieldRequest request
     where
       request = do
@@ -110,8 +117,9 @@
         putByteString value
 
 -- | Remove a record.
-out :: ByteString -- ^ key
-    -> Monarch ()
+out :: (MonadBaseControl IO m, MonadIO m) =>
+       ByteString -- ^ key
+    -> MonarchT m ()
 out key = communicate request response
     where
       request = do
@@ -123,8 +131,9 @@
       response code = throwError code
 
 -- | Retrieve a record.
-get :: ByteString -- ^ key
-    -> Monarch (Maybe ByteString)
+get :: (MonadBaseControl IO m, MonadIO m) =>
+       ByteString -- ^ key
+    -> MonarchT m (Maybe ByteString)
 get key = communicate request response
     where
       request = do
@@ -136,8 +145,9 @@
       response code = throwError code
 
 -- | Retrieve records.
-multipleGet :: [ByteString] -- ^ keys
-            -> Monarch [(ByteString, ByteString)]
+multipleGet :: (MonadBaseControl IO m, MonadIO m) =>
+               [ByteString] -- ^ keys
+            -> MonarchT m [(ByteString, ByteString)]
 multipleGet keys = communicate request response
     where
       request = do
@@ -152,8 +162,9 @@
       response code = throwError code
 
 -- | Get the size of the value of a record.
-valueSize :: ByteString -- ^ key
-          -> Monarch (Maybe Int)
+valueSize :: (MonadBaseControl IO m, MonadIO m) =>
+             ByteString -- ^ key
+          -> MonarchT m (Maybe Int)
 valueSize key = communicate request response
     where
       request = do
@@ -165,7 +176,8 @@
       response code = throwError code
 
 -- | Initialize the iterator.
-iterInit :: Monarch ()
+iterInit :: (MonadBaseControl IO m, MonadIO m) =>
+            MonarchT m ()
 iterInit = communicate request response
     where
       request = putMagic 0x50
@@ -174,7 +186,8 @@
 
 -- | Get the next key of the iterator.
 --   The iterator can be updated by multiple connections and then it is not assured that every record is traversed.
-iterNext :: Monarch (Maybe ByteString)
+iterNext :: (MonadBaseControl IO m, MonadIO m) =>
+            MonarchT m (Maybe ByteString)
 iterNext = communicate request response
     where
       request = putMagic 0x51
@@ -183,9 +196,10 @@
       response code = throwError code
 
 -- | Get forward matching keys.
-forwardMatchingKeys :: ByteString -- ^ key prefix
+forwardMatchingKeys :: (MonadBaseControl IO m, MonadIO m) =>
+                       ByteString -- ^ key prefix
                     -> Maybe Int -- ^ maximum number of keys to be fetched. 'Nothing' means unlimited.
-                    -> Monarch [ByteString]
+                    -> MonarchT m [ByteString]
 forwardMatchingKeys prefix n = communicate request response
     where
       request = do
@@ -201,9 +215,10 @@
 -- | Add an integer to a record.
 --   If the corresponding record exists, the value is treated as an integer and is added to.
 --   If no record corresponds, a new record of the additional value is stored.
-addInt :: ByteString -- ^ key
+addInt :: (MonadBaseControl IO m, MonadIO m) =>
+          ByteString -- ^ key
        -> Int -- ^ value
-       -> Monarch Int
+       -> MonarchT m Int
 addInt key n = communicate request response
     where
       request = do
@@ -217,9 +232,10 @@
 -- | Add a real number to a record.
 --   If the corresponding record exists, the value is treated as a real number and is added to.
 --   If no record corresponds, a new record of the additional value is stored.
-addDouble :: ByteString -- ^ key
+addDouble :: (MonadBaseControl IO m, MonadIO m) =>
+             ByteString -- ^ key
           -> Double -- ^ value
-          -> Monarch Double
+          -> MonarchT m Double
 addDouble key n = communicate request response
     where
       request = do
@@ -232,11 +248,12 @@
       response code = throwError code
 
 -- | Call a function of the script language extension.
-ext :: ByteString -- ^ function
+ext :: (MonadBaseControl IO m, MonadIO m) =>
+       ByteString -- ^ function
     -> [ExtOption] -- ^ option flags
     -> ByteString -- ^ key
     -> ByteString -- ^ value
-    -> Monarch ByteString
+    -> MonarchT m ByteString
 ext func opts key value = communicate request response
     where
       request = do
@@ -252,7 +269,8 @@
       response code = throwError code
 
 -- | Synchronize updated contents with the file and the device.
-sync :: Monarch ()
+sync :: (MonadBaseControl IO m, MonadIO m) =>
+        MonarchT m ()
 sync = communicate request response
     where
       request = putMagic 0x70
@@ -260,8 +278,9 @@
       response code = throwError code
 
 -- | Optimize the storage.
-optimize :: ByteString -- ^ parameter
-         -> Monarch ()
+optimize :: (MonadBaseControl IO m, MonadIO m) =>
+            ByteString -- ^ parameter
+         -> MonarchT m ()
 optimize param = communicate request response
     where
       request = do
@@ -272,7 +291,8 @@
       response code = throwError code
 
 -- | Remove all records.
-vanish :: Monarch ()
+vanish :: (MonadBaseControl IO m, MonadIO m) =>
+          MonarchT m ()
 vanish = communicate request response
     where
       request = putMagic 0x72
@@ -280,8 +300,9 @@
       response code = throwError code
 
 -- | Copy the database file.
-copy :: ByteString -- ^ path
-     -> Monarch ()
+copy :: (MonadBaseControl IO m, MonadIO m) =>
+        ByteString -- ^ path
+     -> MonarchT m ()
 copy path = communicate request response
     where
       request = do
@@ -292,11 +313,11 @@
       response code = throwError code
 
 -- | Restore the database file from the update log.
-restore :: Integral a =>
+restore :: (MonadBaseControl IO m, MonadIO m, Integral a) =>
            ByteString -- ^ path
         -> a -- ^ beginning time stamp in microseconds
         -> [RestoreOption] -- ^ option flags
-        -> Monarch ()
+        -> MonarchT m ()
 restore path usec opts = communicate request response
     where
       request = do
@@ -309,12 +330,12 @@
       response code = throwError code
 
 -- | Set the replication master.
-setMaster :: Integral a =>
+setMaster :: (MonadBaseControl IO m, MonadIO m, Integral a) =>
              ByteString -- ^ host
           -> Int -- ^ port
           -> a -- ^ beginning time stamp in microseconds
           -> [RestoreOption] -- ^ option flags
-          -> Monarch ()
+          -> MonarchT m ()
 setMaster host port usec opts = communicate request response
     where
       request = do
@@ -328,7 +349,8 @@
       response code = throwError code
 
 -- | Get the number of records.
-recordNum :: Monarch Int64
+recordNum :: (MonadBaseControl IO m, MonadIO m) =>
+             MonarchT m Int64
 recordNum = communicate request response
     where
       request = putMagic 0x80
@@ -336,7 +358,8 @@
       response code = throwError code
 
 -- | Get the size of the database.
-size :: Monarch Int64
+size :: (MonadBaseControl IO m, MonadIO m) =>
+        MonarchT m Int64
 size = communicate request response
     where
       request = putMagic 0x81
@@ -344,7 +367,8 @@
       response code = throwError code
 
 -- | Get the status string of the database.
-status :: Monarch ByteString
+status :: (MonadBaseControl IO m, MonadIO m) =>
+          MonarchT m ByteString
 status = communicate request response
     where
       request = putMagic 0x88
@@ -352,10 +376,11 @@
       response code = throwError code
 
 -- | Call a versatile function for miscellaneous operations.
-misc :: ByteString -- ^ function name
+misc :: (MonadBaseControl IO m, MonadIO m) =>
+        ByteString -- ^ function name
      -> [MiscOption] -- ^ option flags
      -> [ByteString] -- ^ arguments
-     -> Monarch [ByteString]
+     -> MonarchT m [ByteString]
 misc func opts args = communicate request response
   where
     request = do
diff --git a/Database/Monarch/MessagePack.hs b/Database/Monarch/MessagePack.hs
--- a/Database/Monarch/MessagePack.hs
+++ b/Database/Monarch/MessagePack.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE FlexibleContexts #-}
 -- | Store/Retrieve a MessagePackable record.
 module Database.Monarch.MessagePack
      (
@@ -11,6 +12,7 @@
 import Data.Binary.Put (putWord32be, putByteString, putLazyByteString)
 import Control.Applicative
 import Control.Monad.Error
+import Control.Monad.Trans.Control
 
 import Database.Monarch.Raw
 import Database.Monarch.Utils
@@ -18,10 +20,10 @@
 -- | Store a record.
 --   If a record with the same key exists in the database,
 --   it is overwritten.
-put :: MsgPack.Packable a =>
+put :: (MonadBaseControl IO m, MonadIO m, MsgPack.Packable a) =>
        ByteString -- ^ key
     -> a -- ^ value
-    -> Monarch ()
+    -> MonarchT m ()
 put key value = communicate request response
     where
       msg = MsgPack.pack value
@@ -37,10 +39,10 @@
 -- | Store a new record.
 --   If a record with the same key exists in the database,
 --   this function has no effect.
-putKeep :: MsgPack.Packable a =>
+putKeep :: (MonadBaseControl IO m, MonadIO m, MsgPack.Packable a) =>
            ByteString -- ^ key
         -> a -- ^ value
-        -> Monarch ()
+        -> MonarchT m ()
 putKeep key value = communicate request response
     where
       msg = MsgPack.pack value
@@ -56,10 +58,10 @@
 
 -- | Store a record without response.
 --   If a record with the same key exists in the database, it is overwritten.
-putNoResponse :: MsgPack.Packable a =>
+putNoResponse :: (MonadBaseControl IO m, MonadIO m, MsgPack.Packable a) =>
                  ByteString -- ^ key
               -> a -- ^ value
-              -> Monarch ()
+              -> MonarchT m ()
 putNoResponse key value = yieldRequest request
     where
       msg = MsgPack.pack value
@@ -71,9 +73,9 @@
         putLazyByteString msg
 
 -- | Retrieve a record.
-get :: MsgPack.Unpackable a =>
+get :: (MonadBaseControl IO m, MonadIO m, MsgPack.Unpackable a) =>
        ByteString -- ^ key
-    -> Monarch (Maybe a)
+    -> MonarchT m (Maybe a)
 get key = communicate request response
     where
       request = do
diff --git a/Database/Monarch/Raw.hs b/Database/Monarch/Raw.hs
--- a/Database/Monarch/Raw.hs
+++ b/Database/Monarch/Raw.hs
@@ -1,11 +1,13 @@
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE UndecidableInstances #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE TypeFamilies #-}
 -- | Raw definitions.
 module Database.Monarch.Raw
     (
-      Monarch
+      Monarch, MonarchT
     , Connection, ConnectionPool
     , withMonarchConn
     , withMonarchPool
@@ -59,24 +61,33 @@
 -- | Options for miscellaneous operation
 data MiscOption = NoUpdateLog -- ^ omission of update log
 
--- | A monad supporting TokyoTyrant access.
-newtype Monarch a =
-    Monarch { unMonarch :: ErrorT Code (ReaderT Connection IO) a }
+-- | The Monarch monad transformer to provide TokyoTyrant access.
+newtype MonarchT m a =
+    MonarchT { unMonarchT :: ErrorT Code (ReaderT Connection m) a }
     deriving ( Functor, Applicative, Monad, MonadIO
-             , MonadReader Connection, MonadError Code, MonadBase IO )
+             , MonadReader Connection, MonadError Code, MonadBase base )
 
-instance MonadBaseControl IO Monarch where
-    newtype StM Monarch a = StMM { unStMM :: StM (ErrorT Code (ReaderT Connection IO)) a }
-    liftBaseWith f = Monarch . liftBaseWith $ \runInBase -> f $ liftM StMM . runInBase . unMonarch
-    restoreM = Monarch . restoreM . unStMM
+instance MonadTrans MonarchT where
+    lift = MonarchT . lift . lift
 
+instance MonadTransControl MonarchT where
+    newtype StT MonarchT a = StMonarch { unStMonarch :: Either Code a }
+    liftWith f = MonarchT . ErrorT . ReaderT $ (\r -> liftM Right (f $ \t -> liftM StMonarch (runReaderT (runErrorT (unMonarchT t)) r)))
+    restoreT = MonarchT . ErrorT . ReaderT . const .liftM unStMonarch
+
+instance MonadBaseControl base m => MonadBaseControl base (MonarchT m) where
+    newtype StM (MonarchT m) a = StMMonarchT { unStMMonarchT :: ComposeSt MonarchT m a }
+    liftBaseWith = defaultLiftBaseWith StMMonarchT
+    restoreM = defaultRestoreM unStMMonarchT
+
+type Monarch = MonarchT IO
+
 -- | Run Monarch with TokyoTyrant at target host and port.
 runMonarch :: MonadIO m =>
               Connection
-           -> Monarch a
+           -> MonarchT m a
            -> m (Either Code a)
-runMonarch conn action =
-    liftIO $ runReaderT (runErrorT $ unMonarch action) conn
+runMonarch conn action = runReaderT (runErrorT $ unMonarchT action) conn
 
 -- | Create a TokyoTyrant connection and run the given action.
 -- Don't use the given 'Connection' outside the action.
@@ -107,27 +118,27 @@
 
 -- | Run action with a connection.
 runMonarchConn :: (MonadBaseControl IO m, MonadIO m) =>
-                  Monarch a
+                  MonarchT m a
                -> Connection
                -> m (Either Code a)
 runMonarchConn action conn = runMonarch conn action
 
 -- | Run action with a unused connection from the pool.
 runMonarchPool :: (MonadBaseControl IO m, MonadIO m) =>
-                  Monarch a
+                  MonarchT m a
                -> ConnectionPool
                -> m (Either Code a)
 runMonarchPool action pool = withResource pool (\conn -> runMonarch conn action)
 
-throwError' :: Code -> SomeException -> Monarch a
+throwError' :: (Monad m) => Code -> SomeException -> MonarchT m a
 throwError' e _ = throwError e
 
-sendLBS :: LBS.ByteString -> Monarch ()
+sendLBS :: (MonadBaseControl IO m, MonadIO m) => LBS.ByteString -> MonarchT m ()
 sendLBS lbs = do
   conn <- connection <$> ask
   liftIO (NSLBS.sendAll conn lbs) `E.catch` throwError' SendError
 
-recvLBS :: Int64 -> Monarch LBS.ByteString
+recvLBS :: (MonadBaseControl IO m, MonadIO m) => Int64 -> MonarchT m LBS.ByteString
 recvLBS n = do
   conn <- connection <$> ask
   lbs <- liftIO (NSLBS.recv conn n) `E.catch` throwError' SendError
diff --git a/Database/Monarch/Utils.hs b/Database/Monarch/Utils.hs
--- a/Database/Monarch/Utils.hs
+++ b/Database/Monarch/Utils.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE FlexibleContexts #-}
 module Database.Monarch.Utils
     (
       toCode
@@ -20,6 +21,8 @@
 import Data.Binary.Put (runPut, putWord32be)
 import Data.Binary.Get (runGet, getWord32be)
 import Control.Applicative
+import Control.Monad.IO.Class
+import Control.Monad.Trans.Control
 
 import Database.Monarch.Raw
 
@@ -67,32 +70,32 @@
 fromLBS :: LBS.ByteString -> BS.ByteString
 fromLBS = BS.pack . LBS.unpack
 
-yieldRequest :: B.Put -> Monarch ()
+yieldRequest :: (MonadBaseControl IO m, MonadIO m) => B.Put -> MonarchT m ()
 yieldRequest = sendLBS . runPut
 
-responseCode :: Monarch Code
+responseCode :: (MonadBaseControl IO m, MonadIO m) => MonarchT m Code
 responseCode = toCode . fromIntegral . runGet B.getWord8 <$> recvLBS 1
 
-parseLBS :: Monarch LBS.ByteString
+parseLBS :: (MonadBaseControl IO m, MonadIO m) => MonarchT m LBS.ByteString
 parseLBS = recvLBS 4 >>=
            recvLBS . fromIntegral . runGet getWord32be
 
-parseBS :: Monarch BS.ByteString
+parseBS :: (MonadBaseControl IO m, MonadIO m) => MonarchT m BS.ByteString
 parseBS = fromLBS <$> parseLBS
 
-parseWord32 :: Monarch B.Word32
+parseWord32 :: (MonadBaseControl IO m, MonadIO m) => MonarchT m B.Word32
 parseWord32 = runGet getWord32be <$> recvLBS 4
 
-parseInt64 :: Monarch Int64
+parseInt64 :: (MonadBaseControl IO m, MonadIO m) => MonarchT m Int64
 parseInt64 = runGet (B.get :: B.Get Int64) <$> recvLBS 8
 
-parseDouble :: Monarch Double
+parseDouble :: (MonadBaseControl IO m, MonadIO m) => MonarchT m Double
 parseDouble = do
   integ <- fromIntegral <$> parseInt64
   fract <- fromIntegral <$> parseInt64
   return $ integ + fract * 1e-12
 
-parseKeyValue :: Monarch (BS.ByteString, BS.ByteString)
+parseKeyValue :: (MonadBaseControl IO m, MonadIO m) => MonarchT m (BS.ByteString, BS.ByteString)
 parseKeyValue = do
   ksiz <- recvLBS 4
   vsiz <- recvLBS 4
@@ -102,9 +105,10 @@
            runGet getWord32be vsiz
   return (fromLBS key, fromLBS value)
 
-communicate :: B.Put
-            -> (Code -> Monarch a)
-            -> Monarch a
+communicate :: (MonadBaseControl IO m, MonadIO m) =>
+               B.Put
+            -> (Code -> MonarchT m a)
+            -> MonarchT m a
 communicate makeRequest makeResponse =
     yieldRequest makeRequest >>
     responseCode >>=
diff --git a/monarch.cabal b/monarch.cabal
--- a/monarch.cabal
+++ b/monarch.cabal
@@ -1,5 +1,5 @@
 name:                monarch
-version:             0.5.0.0
+version:             0.6.0.0
 synopsis:            Monadic interface for TokyoTyrant.
 description:         This package provides simple monadic interface for TokyoTyrant.
 license:             BSD3
@@ -20,6 +20,7 @@
   ghc-options:         -Wall
   build-depends:       base ==4.*
                      , mtl ==2.1.*
+                     , transformers ==0.3.*
                      , bytestring ==0.9.*
                      , network-conduit ==0.5.*
                      , binary ==0.5.*
@@ -37,6 +38,7 @@
   main-is:             test.hs
   build-depends:       base ==4.*
                      , mtl ==2.1.*
+                     , transformers ==0.3.*
                      , bytestring ==0.9.*
                      , network-conduit ==0.5.*
                      , binary ==0.5.*
@@ -55,6 +57,7 @@
   main-is:             benchmark.hs
   build-depends:       base ==4.*
                      , mtl ==2.1.*
+                     , transformers ==0.3.*
                      , bytestring ==0.9.*
                      , binary ==0.5.*
                      , network ==2.3.*
diff --git a/test/test.hs b/test/test.hs
--- a/test/test.hs
+++ b/test/test.hs
@@ -50,7 +50,7 @@
            it "store a record" casePutNrMsgPackRecord
 
 returns :: (Eq a, Show a) =>
-           Monarch a
+           MonarchT IO a
         -> Either Code a
         -> IO ()
 action `returns` expected = connTest >> poolTest