This paper describes a multiregional demoeconomic simulation model for the state of North Rhine-Westphalia in the Federal Republic of Germany. First, basic hypotheses of the model are discussed in the light of relevant theories and confronted with recent trends of regional development. Thereafter, the major submodels of the simulation model and the links between them are discussed in detail. The discussion focuses on two submodels simulating aging and migration of population and the locating behavior of industries.