diff --git a/math/mathcore/inc/Math/PdfFuncMathCore.h b/math/mathcore/inc/Math/PdfFuncMathCore.h
index d6249e7210357747be932b468933f64434651349..00cf35f96d96fa4d63a9e447dd6b0f98bddeb94c 100644
--- a/math/mathcore/inc/Math/PdfFuncMathCore.h
+++ b/math/mathcore/inc/Math/PdfFuncMathCore.h
@@ -262,7 +262,7 @@ namespace Math {
    
    */
 
-   double landau_pdf(double x, double sigma = 1, double x0 = 0.); 
+   double landau_pdf(double x, double s = 1, double x0 = 0.); 
 
 
   /**
@@ -274,7 +274,8 @@ namespace Math {
   for x>0. For detailed description see 
   <A HREF="http://mathworld.wolfram.com/LogNormalDistribution.html">
   Mathworld</A>. 
-
+  @param s scale parameter (not the sigma of the distribution which is not even defined)
+  @param x0  location parameter, corresponds approximatly to the most probable value. For x0 = 0, sigma = 1, the x_mpv = -0.22278
   
   @ingroup PdfFunc
 
diff --git a/math/mathcore/src/PdfFuncMathCore.cxx b/math/mathcore/src/PdfFuncMathCore.cxx
index cf4ff6bd4374a101641c7c4859c4d10df7a74bed..96c8ca3ad57e3cf168fdb0bb2ed49058f22c2b2a 100644
--- a/math/mathcore/src/PdfFuncMathCore.cxx
+++ b/math/mathcore/src/PdfFuncMathCore.cxx
@@ -187,7 +187,7 @@ namespace Math {
          u   = 1/(v-v*std::log(v)/(v+1));
          denlan = u*u*(1+(a2[0]+a2[1]*u)*u);
       }
-      return denlan;
+      return denlan/sigma;
 }
 
       
diff --git a/math/mathcore/src/TMath.cxx b/math/mathcore/src/TMath.cxx
index 5abc8d27e2c5f79231a03e5929cf2d75dd4acb0f..bb2982140e3bf33cefb2bcde2832468ad75a2f72 100644
--- a/math/mathcore/src/TMath.cxx
+++ b/math/mathcore/src/TMath.cxx
@@ -498,12 +498,16 @@ Double_t TMath::Gaus(Double_t x, Double_t mean, Double_t sigma, Bool_t norm)
 //______________________________________________________________________________
 Double_t TMath::Landau(Double_t x, Double_t mpv, Double_t sigma, Bool_t norm)
 {
-   // The LANDAU function with mpv(most probable value) and sigma.
+   // The LANDAU function. 
+   // mpv is a location parameter and correspond approximatly to the most probable value
+   // and sigma is a scale parameter (not the sigma of the full distribution which is not defined)
+   // Note that for mpv=0 and sigma=1 (default values) the exact location of the maximum of the distribution (most proble value) is at 
+   // x = -0.22278
    // This function has been adapted from the CERNLIB routine G110 denlan.
    // If norm=kTRUE (default is kFALSE) the result is divided by sigma
 
    if (sigma <= 0) return 0; 
-   Double_t den = ::ROOT::Math::landau_pdf(x, sigma, mpv); 
+   Double_t den = ::ROOT::Math::landau_pdf( (x-mpv)/sigma ); 
    if (!norm) return den;
    return den/sigma;
 }