Automatic parameterization procedures, which are important components in our latest approach of making transferable and extensible general force fields, were demonstrated by deriving parameters from ab initio and empirical data, and subsequently predicting densities for nine molecular fluids. Excellent agreements with available experimental data were obtained for most of the systems studied. The automated procedure for deriving van der Waals parameters, constructed by combining the molecular dynamics simulation and statistical mechanical perturbation theory, is described. (C) 2003 Elsevier B.V. All rights reserved.