9618057 McLennan Despite the widespread use of game theoretic models in the social sciences, there is as yet no software available to solve computationally game theory problems. This project completed the development and testing of the first computer programs for analysis of extensive and normal form games. The computer code (both source and executable code) that developed under this grant is made available free of charge for use in research and teaching by individuals in the academic community. This new software is opening up the entire field of game theory and all of the social science applications of game theory to computationally intensive research. More specifically, the project develops a computer program for interactively building and finding sample equilibria for extensive form games. It also implements new algorithms for finding all equilibria (for a given refinement of Nash equilibria) for any given extensive form game. The main program will allow for interactive construction of an arbitrary finite extensive form game. It will be able to represent games of incomplete information, as well as certain types of infinitely repeated and stochastic games. For any extensive form game, the program will compute sample equilibria of the game, either on the extensive or normal form, i.e., in behavioral or mixed strategies. In addition to Nash equilibria, the program will be able to compute various refinements of Nash equilibria, such as sequential equilibria, perfect equilibria, proper equilibria, and simple stable sets. One goal of the project is to develop a capability for the program to calculate closed form analytical formulas for an equilibrium as a function of a specified parameter of the problem. ??