Evidenced-based medicine, the new practice paradigm, is rapidly replacing medicine by authority, the traditional paradigm. In 1993, we introduced evidence-based practice into our Department of Obstetrics, Gynecology, and Reproductive Sciences at San Francisco General Hospital, University of California, San Francisco. We orient all fellows, residents, and students to new methods of clinical decision making that use formal rules of evidence. We changed the format of clinical conferences from didactic lectures to clinical problem-solving sessions using the evidence-based medicine approach. Useful resources include the Cochrane Pregnncy and Childbirth Database on computer; Epi Info, version 6, a public-domain software package for microcomputers; 24-hour access to free MEDLINE searchers via the Internet; the ACOG Resource Center; ACOGNET; and several paperback texts on critical appraisal. Evidence-based medicine helps to level the intellectual playing field in an academic department. This approach directly improves patient care by placing practice on a more secure scientific foundation. Moreover, evidence-based medicine provides clinicians with the skills to practice safe and effective obstetrics and gynecology as practice evolves.