A prototype expert system (NERISK) has been developed to help users assess the impact of pesticides on beneficial arthropod predators and parasitoids in agricultural systems. A shell program (RECOG) was adapted with minor modifications to allow the encoding of expert opinion on the topic by persons with minimal computer skills. A procedure was added that allows the user to access databases, simulation models, and other programs from within the expert system, and to use the query and model output as part of an integrated knowledge organization and delivery package. A large database (ca 12,000 records) and several expert opinion components on pesticide effects on natural enemies have been integrated into an easily accessible program. The expert system will help regulatory agents, university research and extension personnel, and production managers make decisions about the integration of pesticides and biological control agents in agricultural production systems.