diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,9 @@
 # Changelog for srtree
 
+## 0.1.2.0
+
+Implemented `deriveParamBy` to calculate the derivative by the parameters indexed by `ix`
+
 ## 0.1.1.0
 
 - Fixed compilation bug
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -21,14 +21,13 @@
 ## Other features:
 
 - simplification algorithm (`simplify`)
-- derivative w.r.t. a variable (`deriveBy`)
+- derivative w.r.t. a variable (`deriveBy`) and w.r.t. a parameter (`deriveParamBy`)
 - evaluation (`evalTree`)
 - relabel free parameters sequentially (`relabelParams`)
 - relabel variables couting their occurrence (`relabelOccurrences`, used with interval arithmetic)
 
 ## TODO:
 
-- derivative w.r.t. free parameters
 - support more advanced functions
 - support conditional branching (`IF-THEN-ELSE`)
 
diff --git a/src/Data/SRTree.hs b/src/Data/SRTree.hs
--- a/src/Data/SRTree.hs
+++ b/src/Data/SRTree.hs
@@ -21,6 +21,7 @@
          , countVarNodes
          , countOccurrences
          , deriveBy
+         , deriveParamBy
          , simplify
          , derivative
          , evalFun
@@ -44,6 +45,7 @@
          , countVarNodes
          , countOccurrences
          , deriveBy
+         , deriveParamBy
          , simplify
          , derivative
          , evalFun
diff --git a/src/Data/SRTree/Internal.hs b/src/Data/SRTree/Internal.hs
--- a/src/Data/SRTree/Internal.hs
+++ b/src/Data/SRTree/Internal.hs
@@ -24,6 +24,7 @@
          , countVarNodes
          , countOccurrences
          , deriveBy
+         , deriveParamBy
          , simplify
          , derivative
          , evalFun
@@ -354,6 +355,34 @@
 deriveBy dx (Power l r)   = l ** (r-1) * (r * deriveBy dx l + l * log l * deriveBy dx r)
 deriveBy dx (LogBase l r) = deriveBy dx (log l / log r)
 {-# INLINE deriveBy #-}
+
+-- | Creates an `SRTree` representing the partial derivative of the input by the parameter indexed by `ix`.
+deriveParamBy :: (Eq ix, Eq val, Floating val, OptIntPow val) => ix -> SRTree ix val -> SRTree ix val
+deriveParamBy _  Empty    = Empty
+deriveParamBy dx (Var ix) = 0
+deriveParamBy dx (Param ix)
+  | dx == ix  = 1
+  | otherwise = 0
+deriveParamBy dx (Const val) = 0
+deriveParamBy dx (Fun g t)   =
+  case deriveParamBy dx t of
+    0  -> 0
+    1  -> derivative g t
+    t' -> derivative g t * t'
+deriveParamBy dx (Pow t 0)   = 0    
+deriveParamBy dx (Pow t 1)   = deriveParamBy dx t
+deriveParamBy dx (Pow t k)   = 
+  case deriveParamBy dx t of
+    0 -> 0
+    Const val -> Const (val * fromIntegral k) * (t ^. (k-1))
+    t'        -> fromIntegral k * (t ^. (k-1)) * t'
+deriveParamBy dx (Add l r)     = deriveParamBy dx l + deriveParamBy dx r
+deriveParamBy dx (Sub l r)     = deriveParamBy dx l - deriveParamBy dx r
+deriveParamBy dx (Mul l r)     = deriveParamBy dx l * r + l * deriveParamBy dx r
+deriveParamBy dx (Div l r)     = (deriveParamBy dx l * r - l * deriveParamBy dx r) / r ^. 2
+deriveParamBy dx (Power l r)   = l ** (r-1) * (r * deriveParamBy dx l + l * log l * deriveParamBy dx r)
+deriveParamBy dx (LogBase l r) = deriveParamBy dx (log l / log r)
+{-# INLINE deriveParamBy #-}
 
 -- | Simplifies the `SRTree`.
 simplify :: (Eq ix, Eq val, Floating val, OptIntPow val) => SRTree ix val -> SRTree ix val
diff --git a/srtree.cabal b/srtree.cabal
--- a/srtree.cabal
+++ b/srtree.cabal
@@ -5,9 +5,9 @@
 -- see: https://github.com/sol/hpack
 
 name:           srtree
-version:        0.1.1.0
+version:        0.1.2.0
 synopsis:       A general framework to work with Symbolic Regression expression trees.
-description:    Please see the README on GitHub at <https://github.com/folivetti/srtree#readme>
+description:    A Symbolic Regression Tree data structure to work with mathematical expressions with support to first order derivative and simplification;
 category:       Math, Data, Data Structures
 homepage:       https://github.com/folivetti/srtree#readme
 bug-reports:    https://github.com/folivetti/srtree/issues