Six widely used computerized drug interaction screening programs were evaluated according to criteria developed by a panel of pharmacists. A panel of six pharmacists from various practice settings developed criteria that were used to evaluate six computerized drug interaction screening programs: Medicom Micro Plus, Medical Letter, S-O-A-P, Drug Interactions by Hansten, Drug Therapy Screening Systems (DTSS), and RxTriage. The criteria were that the programs be user friendly and efficient, provide guidance, and be relevant to the user's practice setting. Also, they should detect interactions, quickly alert the user, and guide the user to the appropriate action. The user should be able to set the level of clinical significance, screen only current drugs in a patient profile, and print out summaries. The panel selected nine known drug interactions to test the programs' knowledge bases. Only Medicom Micro Plus and DTSS detected all nine drug interactions; Medical Letter missed three. RxTriage and Drug Interactions received the highest ratings in user friendliness and efficiency, but both missed two interactions. RxTriage was rated most relevant to their practice by hospital and community pharmacists, and Drug Interactions was rated most relevant by faculty practitioners. S-O-A-P received low ratings overall. Of the six drug interaction screening programs evaluated, none was considered by the panel of pharmacists to be ideal.