In this study, a new simple three-parameter equation is presented for calculation/prediction of the diffusion coefficient of nonelectrolyte organic compounds in water at infinite dilution. The model variables include three molecular-based descriptors. The model is developed using the genetic function approximation (GFA) method. The GFA is applied to select the parameters of the model from more than 3000 molecular-based parameters. To propose a comprehensive and predictive model, 4728 pure chemical compounds are investigated. Furthermore, several statistical methods are implemented to evaluate the predictive power of the model. The root-mean-square of error and the average relative deviation of the model are approximately equal to 3.13 x 10(-6) cm(2).s(-1) and 3.6%.