OBJECTIVE: To recommend effective strategies for implementing clinical practice guidelines (CPGs). DATA SOURCES: The Research and Development Resource Base in Continuing Medical Education, maintained by the University of Toronto, was searched, as was MEDLINE from January 1990 to June 1996, inclusive, with the use of the MeSH heading "practice guidelines" and relevant text words. STUDY SELECTION: Studies of CPG implementation strategies and reviews of such studies were selected. Randomized controlled trials and trials that objectively measured physicians' performance or health care outcomes were emphasized. DATA EXTRACTION: Articles were reviewed to determine the effect of various factors on the adoption of guidelines. DATA SYNTHESIS: The articles showed that CPG dissemination or implementation processes have mixed results. Variables that affect the adoption of guidelines include qualities of the guidelines, characteristics of the health care professional, characteristics of the practice setting, incentives, regulation and patient factors. Specific strategies fell into 2 categories: primary strategies involving mailing or publication of the actual guidelines and secondary interventional strategies to reinforce the guidelines. The interventions were shown to be weak (didactic, traditional continuing medical education and mailings), moderately effective (audit and feedback, especially concurrent, targeted to specific providers and delivered by peers or opinion leaders) and relatively strong (reminder systems, academic detailing and multiple interventions). CONCLUSIONS: The evidence shows serious deficiencies in the adoption of CPGs in practice. Future implementation strategies must overcome this failure through an understanding of the forces and variables influencing practice and through the use of methods that are practice- and community-based rather than didactic.