The overall objectives of the WHIMS project are to (1) provide a framework for testing and applying ongoing research in agroecosystem modeling and decision-making, (2) produce a computer program to help producers, consultants and extension personnel more efficiently manage arthropod pests of cotton and (3) provide estimates of arthropodpest damage as inputs for GOSSYM/COMAX. rbWHIMS, the initial product of the project, is a rule-based expert system built on the WHIMS application framework. It contains some 700 rules and covers nine pest-species groups comprising at least 15 species. The expert system operates by querying the user for field-sampling information, which is then stored in objects representing the corresponding components of the cotton ecosystem. The rule-base then queries these objects to acquire the information needed to render decisions. The rule-base is segmented along insect species groups and cotton plant growth stage. rbWHIMS was evaluated in the field in 1991.