diff --git a/Database/TokyoCabinet/BDB.hs b/Database/TokyoCabinet/BDB.hs
--- a/Database/TokyoCabinet/BDB.hs
+++ b/Database/TokyoCabinet/BDB.hs
@@ -8,6 +8,7 @@
     , ECODE(..)
     , OpenMode(..)
     , TuningOption(..)
+    , CMP(..)
     -- * Basic API (tokyocabinet.idl compliant)
     , new
     , delete
@@ -16,6 +17,7 @@
     , tune
     , setcache
     , setxmsiz
+    , setcmpfunc
     , open
     , close
     , put
@@ -47,6 +49,8 @@
 
 import Data.Int
 import Data.Word
+import Data.ByteString (ByteString)
+import Data.ByteString.Unsafe (unsafePackCStringLen)
 
 import Foreign.Ptr
 import Foreign.ForeignPtr
@@ -106,6 +110,12 @@
 -- @
 --
 
+data CMP = CMPLEXICAL |
+           CMPDECIMAL |
+           CMPINT32 |
+           CMPINT64 |
+           CMP (ByteString -> ByteString -> Ordering)
+
 -- | Create a B+ tree database object. 
 new :: IO BDB
 new = BDB `fmap` (c_tcbdbnew >>= newForeignPtr tcbdbFinalizer)
@@ -147,6 +157,30 @@
 setxmsiz :: BDB -> Int64 -> IO Bool
 setxmsiz bdb xmsiz =
     withForeignPtr (unTCBDB bdb) $ \bdb' -> c_tcbdbsetxmsiz bdb' xmsiz
+
+-- | Set the custom comparison function of a B+ tree database object.
+setcmpfunc :: BDB -> CMP -> IO Bool
+setcmpfunc bdb CMPLEXICAL =
+    withForeignPtr (unTCBDB bdb) $ flip c_tcbdbsetcmpfunc c_tccmplexical
+setcmpfunc bdb CMPDECIMAL =
+    withForeignPtr (unTCBDB bdb) $ flip c_tcbdbsetcmpfunc c_tccmpdecimal
+setcmpfunc bdb CMPINT32 =
+    withForeignPtr (unTCBDB bdb) $ flip c_tcbdbsetcmpfunc c_tccmpint32
+setcmpfunc bdb CMPINT64 =
+    withForeignPtr (unTCBDB bdb) $ flip c_tcbdbsetcmpfunc c_tccmpint64
+setcmpfunc bdb (CMP func) =
+    withForeignPtr (unTCBDB bdb) $ \bdb' ->
+        do cmpfunc <- mkCMP mycmpfunc
+           c_tcbdbsetcmpfunc bdb' cmpfunc
+        where
+          mycmpfunc :: TCCMP'
+          mycmpfunc k1buf k1siz k2buf k2siz _ =
+              do key1 <- unsafePackCStringLen (k1buf, fromIntegral k1siz)
+                 key2 <- unsafePackCStringLen (k2buf, fromIntegral k2siz)
+                 case func key1 key2 of
+                   LT -> return (-1)
+                   EQ -> return 0
+                   GT -> return 1
 
 -- | Open BDB database file.
 open :: BDB -> String -> [OpenMode] -> IO Bool
diff --git a/Database/TokyoCabinet/BDB/C.hsc b/Database/TokyoCabinet/BDB/C.hsc
--- a/Database/TokyoCabinet/BDB/C.hsc
+++ b/Database/TokyoCabinet/BDB/C.hsc
@@ -57,7 +57,7 @@
 combineTuningOption :: [TuningOption] -> Word8
 combineTuningOption = foldr ((.|.) . tuningOptionToWord8) 0
 
-type TCCMP = Ptr CChar -> CInt -> Ptr CChar -> CInt -> Ptr Word8 -> CInt
+type TCCMP' = Ptr CChar -> CInt -> Ptr CChar -> CInt -> Ptr Word8 -> IO CInt
 
 data BDB'
 
@@ -77,7 +77,7 @@
   c_tcbdbsetmutex :: Ptr BDB' -> IO Bool
 
 foreign import ccall safe "tcbdbsetcmpfunc"
-  c_tcbdbsetcmpfunc :: Ptr BDB' -> FunPtr TCCMP -> IO Bool
+  c_tcbdbsetcmpfunc :: Ptr BDB' -> FunPtr TCCMP' -> IO Bool
 
 foreign import ccall safe "tcbdbtune"
   c_tcbdbtune ::
@@ -209,3 +209,18 @@
 
 foreign import ccall safe "tcbdbfsiz"
   c_tcbdbfsiz :: Ptr BDB' -> IO Word64
+
+foreign import ccall safe "tcutil.h &tccmplexical"
+  c_tccmplexical :: FunPtr TCCMP'
+
+foreign import ccall safe "tcutil.h &tccmpdecimal"
+  c_tccmpdecimal :: FunPtr TCCMP'
+
+foreign import ccall safe "tcutil.h &tccmpint32"
+  c_tccmpint32 :: FunPtr TCCMP'
+
+foreign import ccall safe "tcutil.h &tccmpint64"
+  c_tccmpint64 :: FunPtr TCCMP'
+
+foreign import ccall "wrapper"
+  mkCMP :: TCCMP' -> IO (FunPtr TCCMP')
diff --git a/tokyocabinet-haskell.cabal b/tokyocabinet-haskell.cabal
--- a/tokyocabinet-haskell.cabal
+++ b/tokyocabinet-haskell.cabal
@@ -1,10 +1,11 @@
 Name:           tokyocabinet-haskell
-Version:        0.0.2
+Version:        0.0.3
 Cabal-Version:  >= 1.2
 License:        BSD3
 License-File:   LICENSE
 Author:         Tom Tsuruhara
 Maintainer:     tom.lpsd@gmail.com
+Homepage:       http://tom-lpsd.github.com/tokyocabinet-haskell/
 Stability:      experimental
 Category:       Database
 Synopsis:       Haskell binding of Tokyo Cabinet