Recent advances in microprocessor technology have allowed extensive crop growth simulations to be run on desktop microcomputer. One of these programs is a cotton management expert system being implemented throughout the Cotton Belt. GOSSYM-COMAX has been under development by USDA/ARS researchers in Mississippi for several years. This system uses a computer model of a cotton plant called GOSSYM (Gossypium simulation) to simulate the growth of a cotton plant under different conditions and management practices. The expert systems component, COMAX, was recently added to make repeated executions of the GOSSYM model under slightly changing conditions to determine what practices should be used to maximize the yield. This paper describes the initial evaluation of GOSSYM-COMAX under Texas growing conditions. Problems and successes with the model and the expert system are discussed. Major events in the plant growth are noted and compared with model predictions. The expert system recommendations for nitrogen and irrigation water applications were followed and yields are compared to check plots managed according to farmer's practices.