The simulation model presented here for use in urban renewal planning in Sun Francisco is particularly notable for the detailed attention it gives to the atomistic decision-making process which leads to changes of occupancy and the state of the housing stock in large cities. After discussing the objectives of building the model in terms of the uses to which it will be put, the authors describe this simulation of private market decisions and public policy impacts in some detail. The absence of any transportation and accessibility considerations in this paper is worthy of note. It may be explained in part by the very small geographical extent of Sun Francisco and in part by the meticulous attention which is given to other aspects of the housing market influencing residential choice. This paper may be usefully compared with the one by Step and with an article on the New York City Community Renewal Program which will appear in the August issue.