The poor translation of evidence into practice is a well-known problem. Hopes are high that information technology can help make evidence-based practice feasible for mere mortal physicians. In this paper, we draw upon the methods and perspectives of clinical practice, medical informatics, and health services research to analyze the gap between evidence and action, and to argue that computing systems for bridging this gap should incorporate both informatics and health services research expertise. We discuss 2 illustrative systems--trial banks and a web-based system to develop and disseminate evidence-based guidelines (alchemist)--and conclude with a research and training agenda.