diff --git a/Data/Groupoid.hs b/Data/Groupoid.hs
new file mode 100644
--- /dev/null
+++ b/Data/Groupoid.hs
@@ -0,0 +1,9 @@
+module Data.Groupoid
+  ( Groupoid(..)
+  ) where
+
+import Data.Semigroupoid
+
+-- | semigroupoid with inverses. This technically should be a category with inverses, except we need to use Ob to define the valid objects for the category
+class Semigroupoid k => Groupoid k where
+  inv :: k a b -> k b a
diff --git a/Data/Groupoid/Isomorphism.hs b/Data/Groupoid/Isomorphism.hs
new file mode 100644
--- /dev/null
+++ b/Data/Groupoid/Isomorphism.hs
@@ -0,0 +1,21 @@
+module Data.Groupoid.Isomorphism
+  ( Iso(..)
+  ) where
+
+import Data.Semigroupoid
+import Data.Groupoid
+import Control.Category
+import Prelude ()
+
+data Iso k a b = Iso { embed :: k a b, project :: k b a } 
+
+instance Semigroupoid k => Semigroupoid (Iso k) where
+  Iso f g `o` Iso h i = Iso (f `o` h) (i `o` g) 
+
+instance Semigroupoid k => Groupoid (Iso k) where
+  inv (Iso f g) = Iso g f 
+
+instance Category k => Category (Iso k) where
+  Iso f g . Iso h i = Iso (f . h) (i . g) 
+  id = Iso id id 
+
diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,30 @@
+Copyright 2011 Edward Kmett
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+
+1. Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in the
+   documentation and/or other materials provided with the distribution.
+
+3. Neither the name of the author nor the names of his contributors
+   may be used to endorse or promote products derived from this software
+   without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
+IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
diff --git a/Setup.lhs b/Setup.lhs
new file mode 100644
--- /dev/null
+++ b/Setup.lhs
@@ -0,0 +1,7 @@
+#!/usr/bin/runhaskell
+> module Main (main) where
+
+> import Distribution.Simple
+
+> main :: IO ()
+> main = defaultMain
diff --git a/groupoids.cabal b/groupoids.cabal
new file mode 100644
--- /dev/null
+++ b/groupoids.cabal
@@ -0,0 +1,32 @@
+name:          groupoids
+category:      Control, Categories
+version:       0.1
+license:       BSD3
+cabal-version: >= 1.6
+license-file:  LICENSE
+author:        Edward A. Kmett
+maintainer:    Edward A. Kmett <ekmett@gmail.com>
+stability:     experimental
+homepage:      http://github.com/ekmett/groupoids/
+copyright:     Copyright (C) 2011 Edward A. Kmett
+synopsis:      Haskell 98 Groupoids
+description:   Haskell 98 Groupoids
+build-type:    Simple
+
+source-repository head
+  type: git
+  location: git://github.com/ekmett/groupoids.git
+
+library
+  build-depends: 
+    base >= 4 && < 5,
+    semigroupoids >= 1.2.2 && <= 1.3
+
+  exposed-modules:
+    Data.Groupoid
+    Data.Groupoid.Isomorphism
+
+  ghc-options:      -Wall 
+--  if impl(ghc)
+--    cpp-options: -DGHC_TYPEABLE
+--  extensions: CPP