A general methodology for Computer Aided Product Design (CAPD) with specified property constraints which is capable of solving a large range of problems is presented. The methodology employs the group contribution approach, generates acyclic, cyclic and aromatic compounds of various degrees of complexity (including isomers) and size (including polymers) and provides accurate and consistent estimation of properties. The application range of the methodology has been enlarged and the validity of the predictions improved through the incorporation of a new group contribution based method for estimation of properties. Also, with new problem formulations, it is possible to consider the formation of azeotropes and the miscibility of mixtures for the substitution of compounds, the design of polymers and the design of solvents for extraction operations involving vapor-liquid equilibria (VLE), liquid-liquid equilibria (LLE), solid-liquid equilibria (SLE) and gas solubility. Finally, a computer program based on the extended methodology has been developed and the results from five case studies highlighting various features of the methodology are presented.