diff --git a/CHANGES b/CHANGES
--- a/CHANGES
+++ b/CHANGES
@@ -18,3 +18,10 @@
 0.1.0.5:
 		added multifit to Numeric.GSL.Fitting.Linear
 		attempt to fix problem on hackage with configure (removed printCurrentDirectory)
+
+0.2.0.1:
+		moved GSL.* to hmatrix-gsl-stats
+		added Numeric.Statistics.Shannon
+
+0.2.0.3:
+		added mutual_information to Numeric.Statistics.Shannon
diff --git a/hstatistics.cabal b/hstatistics.cabal
--- a/hstatistics.cabal
+++ b/hstatistics.cabal
@@ -1,5 +1,5 @@
 Name:               hstatistics
-Version:            0.2.0.2
+Version:            0.2.0.3
 License:            GPL
 License-file:       LICENSE
 Copyright:          (c) A.V.H. McPhail 2010
@@ -22,7 +22,7 @@
 library
 
     Build-Depends:      base >= 3 && < 5,
-                        hmatrix >= 0.9.3, hmatrix-gsl-stats >= 0.1.0.1
+                        hmatrix >= 0.9.3, hmatrix-gsl-stats >= 0.1.0.2
 
     Extensions:         
 
diff --git a/lib/Numeric/Statistics/Shannon.hs b/lib/Numeric/Statistics/Shannon.hs
--- a/lib/Numeric/Statistics/Shannon.hs
+++ b/lib/Numeric/Statistics/Shannon.hs
@@ -14,28 +14,37 @@
 -----------------------------------------------------------------------------
 
 module Numeric.Statistics.Shannon (
-                         entropy
-                         ) where
+                                   entropy
+                                   , mutual_information
+                                  ) where
 
 
 import Data.Packed.Vector
 
-import Numeric.GSL.Histogram hiding(sum)
+import qualified Numeric.GSL.Histogram as H
+import qualified Numeric.GSL.Histogram2D as H2
 
 import Numeric.LinearAlgebra.Algorithms
 import Numeric.LinearAlgebra.Interface()
 
 import Prelude hiding (sum)
 
-sum x = dot x (constant  1 (dim x))
-
-prob p y = let Just y' = find p y 
-           in getBin p y'
+sum x = dot x (constant 1.0 (dim x))
 
 -- | the entropy \sum p_i l\ln{p_i} of a sequence
-entropy :: Histogram             -- the underlying distribution
+entropy :: H.Histogram             -- the underlying distribution
         -> Vector Double         -- the sequence (expected to fall within bounds of Histogram)
         -> Double                -- the entropy
-entropy p x = let ps = mapVector (prob p) x
+entropy p x = let ps = H.prob p x
               in sum (ps * log ps) 
 
+-- | the mutuaal information \sum_x \sum_y \ln{\frac{p(x,y)}{p(x)p(y)}}
+mutual_information :: H2.Histogram2D -- the underlying distribution
+                   -> H.Histogram   -- the first dimension distribution
+                   -> H.Histogram   -- the second dimension distribution
+                   -> (Vector Double, Vector Double) -- the sequence (expected to fall within bounds of Histogram)
+                   -> Double      -- the mutual information
+mutual_information p px py z@(x,y) = let ps = H2.prob p z
+                                         xs = H.prob px x
+                                         ys = H.prob py y
+                               in sum $ log (ps/(xs*ys))