CASE, an artificial intelligence system with demonstrated ability to predict biological activity based on structural considerations, correctly predicts animal carcinogenicity. It can, therefore, play a pivotal role in classifying chemicals as carcinogens and prioritizing them for further testing. Additionally, CASE shows promise in the design of pharmacologically active agents by reducing the number of drugs that need to be synthesized and tested. For both of these applications, CASE provides a mechanism to conserve animal and other testing resources.