Abstract: In this work identity of general logarithmic normal forms is discussed for simulating the molecular weight distribution of polymers. Equations are derived to calculate the moments of and the averages of molecular weights. It substantiates that all forms of logarithmic normal distributions are essentially identical if paramer estimates satisfy certain conditions. In consequence it shows that Wesslau's and Koningsveld's distributions are identical, and that it is impossible to modify simulation peak width and peak location in GPC by varing the distribution index in general logarithmic normal distribution.