This monograph is about the multi regional input-output model used in long-run simulation. The input-output technique was originally developed for spaceless, short-term analysis of a national economy. However, its high potential as an analytical tool has resulted in an expansion of its application in various directions. Thus, we now have the inter- and mul tiregional input-output model, in which a nation is broken down into a number of interacting regions, and some applications dealing with long-range projections of input-output systems. This study attempts to integrate those two directions within the framework of interregional simulation modeling. A major problem with the multiregional input-output model for long-run simulation is how to update the technical and trade coefficients in the model. This study focuses on the trade coefficient updating problem, and a solution is presented in which a trade coefficient model is coupled with the price model built into the input-output system. When I began this project, the main problem facing me was not purely theoretical but a very practical one: how to design an interregional model for Indonesia. Indonesia is a country characterized by its quite uneven population distribution over the archipelago. My interest was in the formation of its settlement policy, and the use of modeling to assist in this process. This original intention may be evident in various parts of the text.