diff --git a/fb-persistent.cabal b/fb-persistent.cabal
--- a/fb-persistent.cabal
+++ b/fb-persistent.cabal
@@ -1,5 +1,5 @@
 name:              fb-persistent
-version:           0.1.2
+version:           0.1.3
 license:           BSD3
 license-file:      LICENSE
 author:            Felipe Lessa
@@ -33,3 +33,5 @@
       base       >= 4     && < 5
     , fb         >= 0.7.1
     , persistent >= 0.7   && < 0.10
+    , cereal     == 0.3.*
+    , time       == 1.4.*
diff --git a/src/Facebook/Persistent.hs b/src/Facebook/Persistent.hs
--- a/src/Facebook/Persistent.hs
+++ b/src/Facebook/Persistent.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE OverloadedStrings, GADTs #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 -- | This package is meant to be imported as
 --
@@ -8,13 +8,22 @@
 -- the following orphan instances:
 --
 -- @
--- instance "PersistField" "Action" -- since 0.1
+-- instance 'PersistField' 'Action'          -- since 0.1
+-- instance 'PersistField' 'Id'              -- since 0.1.2
+-- instance 'PersistField' 'AppAccessToken'  -- since 0.1.3
+-- instance 'PersistField' 'UserAccessToken' -- since 0.1.3
 -- @
 module Facebook.Persistent () where
 
-import Control.Applicative ((<$>))
+import Control.Applicative ((<$>), (<*>))
+import Data.String (fromString)
+import Data.Int (Int64)
+import Data.Word (Word8)
 import Database.Persist
 import Facebook
+import qualified Data.Serialize as S
+import qualified Data.Time.Clock as T
+import qualified Data.Time.Clock.POSIX as T
 
 -- | From @fb-persistent@.  Since 0.1.
 instance PersistField Action where
@@ -35,3 +44,69 @@
     fromPersistValue v = Id <$> fromPersistValue v
     sqlType = sqlType . idCode
     isNullable _ = False
+
+
+-- | From @fb-persistent@.  Since 0.1.3.  Note that your fields
+-- should either be of type 'UserAccessToken' or
+-- 'AppAccessToken', not a polymorphic @'AccessToken' kind@.
+-- Expiration time of 'UserAccessToken'@s@ is saved with
+-- precision of one second.
+instance AccessTokenKind kind => PersistField (AccessToken kind) where
+    toPersistValue = toPersistValue . S.runPut . accessTokenPut
+    fromPersistValue v = do
+      bs <- fromPersistValue v
+      either (Left . fromString) Right (S.runGet accessTokenGet bs)
+    sqlType = sqlType . S.runPut . accessTokenPut
+    isNullable _ = False
+
+
+-- | Since 'AccessToken' is a GADT, our 'S.get' function needs a
+-- type class in order to be implemented.  Which 'accessTokenGet'
+-- gets used is chosen in compile-time.  As a bonus, we implement
+-- 'S.put' in the same way.
+class AccessTokenKind kind where
+  accessTokenPut :: AccessToken kind -> S.Put
+  accessTokenGet :: S.Get (AccessToken kind)
+
+instance AccessTokenKind UserKind where
+  accessTokenPut (UserAccessToken uid token expires) = do
+    S.putWord8 0
+    S.put uid
+    S.put token
+    putUTCTime expires
+  accessTokenGet = do
+    v <- S.getWord8
+    case v of
+      0 -> UserAccessToken <$> S.get <*> S.get <*> getUTCTime
+      1 -> fail $ "fb-persistent: AccessToken: tried to decode an AppAccessToken as UserAccessToken."
+      _ -> accessTokenUnknownVersion v
+
+instance AccessTokenKind AppKind where
+  accessTokenPut (AppAccessToken token) = do
+    S.putWord8 1
+    S.put token
+  accessTokenGet = do
+    v <- S.getWord8
+    case v of
+      1 -> AppAccessToken <$> S.get
+      0 -> fail $ "fb-persistent: AccessToken: tried to decode an UserAccessToken as AppAccessToken."
+      _ -> accessTokenUnknownVersion v
+
+
+putUTCTime :: T.UTCTime -> S.Put
+putUTCTime = S.put . toInt64 . T.utcTimeToPOSIXSeconds
+  where
+    toInt64 :: T.POSIXTime -> Int64
+    toInt64 = truncate
+
+getUTCTime :: S.Get T.UTCTime
+getUTCTime = T.posixSecondsToUTCTime . fromInt64 <$> S.get
+  where
+    fromInt64 :: Int64 -> T.POSIXTime
+    fromInt64 = fromIntegral
+
+
+accessTokenUnknownVersion :: Monad m => Word8 -> m a
+accessTokenUnknownVersion v =
+  fail $ "fb-persistent: AccessToken: unknown version " ++ show v ++
+         ", are you using different versions of fb-persistent?"