A market exchange simulation utilizing the PLATO computer-assisted instructional system at the University of Illinois has been designed to teach students the principles of a general equilibrium system. It serves a laboratory function which supplements traditional instruction by stimulating students' interests and providing them with illustrations of theoretical concepts. The model simulates a simple exchange economy; students order commodities and the computer computes the demands in each market, adjusting prices to supplies and demands. The process is then repeated until equilibrium is reached--i.e., until demands equal supplies. The course instructors provide post-simulation analysis and exposition by methods of their own choice. The simulation was generally well-received in the first course in which it was used, but formal validation remains to be undertaken in the future. (PB)