Abstract The prospects for a substained development in the urea industry are much brighter today than they have been for many years. Demands for energy conservation and environmental control must be answered by the urea process licensors. Snamprogetti, a leader in the urea industry, has promoted an intensive R & D program to fulfil these requirements. The setting-up of a steady state, block structured simulation program was part of this development. A new phase model for the ammonia carbon dioxide-urea-water system at urea synthesis conditions has also been developed. Detailed models for apparatus specific to the urea process such as reactors, carbon dioxide strippers, ammonia strippers, etc. have been included in the generalized simulation program. A powerful convergence promoter based on the evolutionary approach has been used to solve the recycle problems. The simulation program has been verified against experimental data obtained from industrial plants in a full range of process conditions. Simulation results for the H.P. urea synthesis loops of the Snamprogetti ammonia stripping process and the Stamicarbon CO2 stripping process are presented.