Clinical practice guidelines can improve health care outcomes, but they are only as effective as their implementation. We present a framework for implementing practice guidelines that begins by identifying the forces driving and restraining the adoption of the guideline. Strategies for changing physician behavior that strengthen the driving forces and weaken the restraining forces can then be incorporated into a comprehensive implementation program. Nine strategies for changing physician behavior are presented, based on a review of the literature and organizational experience at Group Health Cooperative of Puget Sound. In designing an implementation strategy, it is essential that the resources allocated to implementation are commensurate with the improvement in outcomes expected from the successful implementation of the guideline. All implementation programs should include plans for measuring outcomes to allow for continuing improvement. Guideline implementation, evaluation and improvement efforts are most likely to be successful when they are part of an explicit, evidence-based process for evaluating and improving clinical practice.