diff --git a/changelog b/changelog
--- a/changelog
+++ b/changelog
@@ -1,3 +1,9 @@
+1.2.2
+
+* Implement Either instances for ReviewFailure, AsFailure, ReviewSuccess,
+  and AsSuccess
+* Add hedgehog property tests for Either optic instances
+
 1.2.1
 
 * Updates to documentation.
diff --git a/src/Data/Validation.hs b/src/Data/Validation.hs
--- a/src/Data/Validation.hs
+++ b/src/Data/Validation.hs
@@ -10,7 +10,7 @@
 {-# LANGUAGE NoImplicitPrelude #-}
 {-# OPTIONS_GHC -Wall #-}
 
--- $setup
+-- \$setup
 -- >>> import Prelude hiding (either, id, (.))
 -- >>> import Data.List.NonEmpty(NonEmpty(..))
 -- >>> import Data.Semigroup(Semigroup((<>)))
@@ -96,7 +96,7 @@
 import Control.Arrow (Arrow (arr, first), ArrowApply (app), ArrowChoice (left, right))
 import Control.Category (Category (..), (>>>))
 import Control.DeepSeq (NFData (rnf))
-import Control.Lens (Getter, Lens', Prism, Prism', Review, Wrapped (_Wrapped', type Unwrapped), Rewrapped, prism, prism')
+import Control.Lens (Getter, Lens', Prism, Prism', Review, Rewrapped, Wrapped (_Wrapped', type Unwrapped), prism, prism')
 import Control.Lens.Iso (Iso, iso
 #if !MIN_VERSION_lens(4,20,0)
                        , Swapped(..))
@@ -495,6 +495,20 @@
   reviewFailure = __Failure
   {-# INLINE reviewFailure #-}
 
+-- |
+-- >>> import Control.Lens((#))
+-- >>> reviewFailure # "err" :: Either String Int
+-- Left "err"
+instance ReviewFailure (Either a b) a b where
+  reviewFailure =
+    prism'
+      Left
+      ( \case
+          Left a -> Just a
+          Right _ -> Nothing
+      )
+  {-# INLINE reviewFailure #-}
+
 -- | Class for types that have a 'Prism'' to an @err@ (as generated by @makeClassyPrisms@).
 class (ReviewFailure s err a) => AsFailure s err a | s -> err a where
   _Failure :: Prism' s err
@@ -513,6 +527,26 @@
   _Failure = __Failure
   {-# INLINE _Failure #-}
 
+-- |
+-- >>> import Control.Lens((^?), (#))
+-- >>> _Failure # "err" :: Either String Int
+-- Left "err"
+--
+-- >>> (Left "err" :: Either String Int) ^? _Failure
+-- Just "err"
+--
+-- >>> (Right 1 :: Either String Int) ^? _Failure
+-- Nothing
+instance AsFailure (Either a b) a b where
+  _Failure =
+    prism'
+      Left
+      ( \case
+          Left a -> Just a
+          Right _ -> Nothing
+      )
+  {-# INLINE _Failure #-}
+
 -- | Class for types that have a 'Getter' to an @a@.
 class GetSuccess s err a | s -> err a where
   getSuccess :: Getter s a
@@ -527,6 +561,20 @@
 
 -- |
 -- >>> import Control.Lens((#))
+-- >>> reviewSuccess # 1 :: Either String Int
+-- Right 1
+instance ReviewSuccess (Either a b) a b where
+  reviewSuccess =
+    prism'
+      Right
+      ( \case
+          Right a -> Just a
+          Left _ -> Nothing
+      )
+  {-# INLINE reviewSuccess #-}
+
+-- |
+-- >>> import Control.Lens((#))
 -- >>> reviewSuccess # 1 :: Validation String Int
 -- Success 1
 instance ReviewSuccess (Validation err a) err a where
@@ -536,6 +584,26 @@
 -- | Class for types that have a 'Prism'' to an @a@ (as generated by @makeClassyPrisms@).
 class (ReviewSuccess s err a) => AsSuccess s err a | s -> err a where
   _Success :: Prism' s a
+
+-- |
+-- >>> import Control.Lens((^?), (#))
+-- >>> _Success # 1 :: Either String Int
+-- Right 1
+--
+-- >>> (Right 1 :: Either String Int) ^? _Success
+-- Just 1
+--
+-- >>> (Left "err" :: Either String Int) ^? _Success
+-- Nothing
+instance AsSuccess (Either a b) a b where
+  _Success =
+    prism'
+      Right
+      ( \case
+          Right a -> Just a
+          Left _ -> Nothing
+      )
+  {-# INLINE _Success #-}
 
 -- |
 -- >>> import Control.Lens((^?), (#))
diff --git a/test/hedgehog_tests.hs b/test/hedgehog_tests.hs
--- a/test/hedgehog_tests.hs
+++ b/test/hedgehog_tests.hs
@@ -62,7 +62,15 @@
           ("prop_validator_semigroupoid_assoc", prop_validator_semigroupoid_assoc),
           ("prop_validator_apply_accumulates", prop_validator_apply_accumulates),
           ("prop_validator_alt_accumulates", prop_validator_alt_accumulates),
-          ("prop_validator_alt_left_success", prop_validator_alt_left_success)
+          ("prop_validator_alt_left_success", prop_validator_alt_left_success),
+          ("prop_either_reviewFailure", prop_either_reviewFailure),
+          ("prop_either_asFailure_hit", prop_either_asFailure_hit),
+          ("prop_either_asFailure_miss", prop_either_asFailure_miss),
+          ("prop_either_reviewSuccess", prop_either_reviewSuccess),
+          ("prop_either_asSuccess_hit", prop_either_asSuccess_hit),
+          ("prop_either_asSuccess_miss", prop_either_asSuccess_miss),
+          ("prop_either_failure_roundtrip", prop_either_failure_roundtrip),
+          ("prop_either_success_roundtrip", prop_either_success_roundtrip)
         ]
 
   unless result exitFailure
@@ -384,3 +392,62 @@
     let f = Validator (Success . (+ 1)) :: Validator' [String] Int Int
         g = Validator (\_ -> Failure ["e2"]) :: Validator' [String] Int Int
     runV (f <!> g) x === Success (x + 1)
+
+-- Either instances: ReviewFailure, AsFailure, ReviewSuccess, AsSuccess
+
+genEither :: Gen a -> Gen b -> Gen (Prelude.Either a b)
+genEither ga gb = Gen.choice [fmap Left ga, fmap Right gb]
+
+prop_either_reviewFailure :: Property
+prop_either_reviewFailure =
+  property $ do
+    e <- forAll genStrings
+    (reviewFailure # e :: Prelude.Either [String] Int) === Left e
+
+prop_either_asFailure_hit :: Property
+prop_either_asFailure_hit =
+  property $ do
+    e <- forAll genStrings
+    (Left e :: Prelude.Either [String] Int) ^? _Failure === Just e
+
+prop_either_asFailure_miss :: Property
+prop_either_asFailure_miss =
+  property $ do
+    a <- forAll genInt
+    (Right a :: Prelude.Either [String] Int) ^? _Failure === Nothing
+
+prop_either_reviewSuccess :: Property
+prop_either_reviewSuccess =
+  property $ do
+    a <- forAll genInt
+    (reviewSuccess # a :: Prelude.Either [String] Int) === Right a
+
+prop_either_asSuccess_hit :: Property
+prop_either_asSuccess_hit =
+  property $ do
+    a <- forAll genInt
+    (Right a :: Prelude.Either [String] Int) ^? _Success === Just a
+
+prop_either_asSuccess_miss :: Property
+prop_either_asSuccess_miss =
+  property $ do
+    e <- forAll genStrings
+    (Left e :: Prelude.Either [String] Int) ^? _Success === Nothing
+
+prop_either_failure_roundtrip :: Property
+prop_either_failure_roundtrip =
+  property $ do
+    x <- forAll (genEither genStrings genInt)
+    let reviewed = x ^? _Failure
+    case x of
+      Left e -> reviewed === Just e
+      Right _ -> reviewed === Nothing
+
+prop_either_success_roundtrip :: Property
+prop_either_success_roundtrip =
+  property $ do
+    x <- forAll (genEither genStrings genInt)
+    let reviewed = x ^? _Success
+    case x of
+      Right a -> reviewed === Just a
+      Left _ -> reviewed === Nothing
diff --git a/validation.cabal b/validation.cabal
--- a/validation.cabal
+++ b/validation.cabal
@@ -1,5 +1,5 @@
 name:               validation
-version:            1.2.1
+version:            1.2.2
 license:            BSD3
 license-file:       LICENCE
 author:             Tony Morris <ʇǝu˙sıɹɹoɯʇ@ןןǝʞsɐɥ> <dibblego>, Nick Partridge <nkpart>