diff --git a/Data/LargeWord.hs b/Data/LargeWord.hs
--- a/Data/LargeWord.hs
+++ b/Data/LargeWord.hs
@@ -31,6 +31,9 @@
 import Numeric
 import Data.Char
 
+import Control.Applicative ((<$>), (<*>))
+import Data.Binary (Binary, put, get)
+
 -- Keys have certain capabilities.
 
 class LargeWord a where
@@ -233,6 +236,10 @@
 	pred (LargeKey l h) = LargeKey (pred l) h
 	succ (LargeKey l h) = if l == maxBound then LargeKey 0 (succ h)
                                                else LargeKey (succ l) h
+
+instance (Binary a, Binary b) => Binary (LargeKey a b) where
+   put (LargeKey lo hi) = put hi >> put lo
+   get = flip LargeKey <$> get <*> get
 
 type Word96  = LargeKey Word32 Word64
 type Word128 = LargeKey Word64 Word64
diff --git a/Tests/Properties.hs b/Tests/Properties.hs
--- a/Tests/Properties.hs
+++ b/Tests/Properties.hs
@@ -8,6 +8,8 @@
 import Data.LargeWord
 import Data.Bits
 import Control.Monad
+import Data.Binary (encode, decode, Binary)
+import qualified Data.ByteString.Lazy as LZ
 
 instance (Arbitrary a, Arbitrary b) => Arbitrary (LargeKey a b) where
    arbitrary = liftM2 LargeKey arbitrary arbitrary
@@ -17,10 +19,28 @@
 
 u1 = shiftR (18446744073709551616  :: Word128) 64  @?= 1
 
+encodeDecode :: (Binary a, Binary b, Eq a, Eq b) => LargeKey a b -> Bool
+encodeDecode word = decode encoded == word
+	where
+	encoded = encode word
+	{-# NOINLINE encoded #-}
+
+correctEncoding = (decode . LZ.pack)
+	[0,0,0,0,0,0,0,0,50,89,125,125,237,119,73,240,217,12,178,101,235,8,44,221,50,122,244,125,115,181,239,78]
+	@?=
+	(1234567891234567891234567812345678123456781234567812345678 :: Word256)
+
 tests :: [Test]
 tests =
     [ testProperty "largeword shift left then right" pShiftRightShiftLeft
     , testCase "largeword shift 2^64 by 2^64" u1
+    , testCase "big-endian encoding" correctEncoding
+    , testProperty "Word96 encode/decode loop" (encodeDecode::Word96 -> Bool)
+    , testProperty "Word128 encode/decode loop" (encodeDecode::Word128 -> Bool)
+    , testProperty "Word160 encode/decode loop" (encodeDecode::Word160 -> Bool)
+    , testProperty "Word192 encode/decode loop" (encodeDecode::Word192 -> Bool)
+    , testProperty "Word224 encode/decode loop" (encodeDecode::Word224 -> Bool)
+    , testProperty "Word256 encode/decode loop" (encodeDecode::Word256 -> Bool)
       ]
 
 main = defaultMain tests
diff --git a/largeword.cabal b/largeword.cabal
--- a/largeword.cabal
+++ b/largeword.cabal
@@ -1,5 +1,5 @@
 name:           largeword
-version:        1.0.5
+version:        1.1.0
 license:        BSD3
 copyright:      Dominic Steinitz <dominic@steinitz.org>
 author:         Dominic Steinitz <dominic@steinitz.org>
@@ -21,7 +21,8 @@
     location: https://github.com/idontgetoutmuch/largeword
 
 Library
-  Build-Depends:   base >= 4.0 && < 5
+  Build-Depends:   base >= 4.0 && < 5,
+                   binary
   exposed-modules: Data.LargeWord
 
 Test-suite tests
@@ -29,6 +30,8 @@
   Hs-source-dirs: Tests
   Main-is: Properties.hs
   Build-depends: base >= 4.0 && < 5,
+                 binary,
+                 bytestring,
                  test-framework >= 0.3.3 && < 0.9,
                  test-framework-quickcheck2 >= 0.2.9 && < 0.4,
                  test-framework-hunit >= 0.2.6 && < 0.4,