Increasing recognition of the failure to translate research findings into practice has led to greater awareness of the importance of using active dissemination and implementation strategies. Although there is a growing body of research evidence about the effectiveness of different strategies, this is not easily accessible to policy makers and professionals. To identify, appraise, and synthesize systematic reviews of professional educational or quality assurance interventions to improve quality of care. An overview was made of systematic reviews of professional behavior change interventions published between 1966 and 1998. Forty-one reviews were identified covering a wide range of interventions and behaviors. In general, passive approaches are generally ineffective and unlikely to result in behavior change. Most other interventions are effective under some circumstances; none are effective under all circumstances. Promising approaches include educational outreach (for prescribing) and reminders. Multifaceted interventions targeting different barriers to change are more likely to be effective than single interventions. Although the current evidence base is incomplete, it provides valuable insights into the likely effectiveness of different interventions. Future quality improvement or educational activities should be informed by the findings of systematic reviews of professional behavior change interventions.