This paper describes the background and methods of an Agency for Healthcare Research and Quality-funded study designed to evaluate the impact of a quality improvement model using academic detailing and electronic medical records (EMRs) on adherence with 22 clinical practice guidelines for prevention of cardiovascular disease and stroke. The study is being conducted in 23 primary care practices in 14 states that use a common EMR and pool data for research. Control practices receive copies of the clinical practice guidelines and quarterly updates of their adherence with them. Intervention practices receive similar information and participate in regular site visits and investigator meetings designed to catalyze their quality improvement efforts. The intervention began January 1, 2001 and will be completed on June 30, 2003.