In order to improve compliance with the National Cancer Institute's breast cancer screening guidelines, we developed a multifaceted intervention designed to alter physician screening practice. A pre-post test, two-community design was used. Primary care physicians in one community served as the control. Data were collected by two mailed surveys (1987 and 1990). Response rates were 61% and 64%, respectively. The physician intervention program consisted of a hospital-based continuing medical education program and an outreach component which focused on implementing a reminder system. Outcome measures were self-reported attitudinal, knowledge, and screening practices changes. In spite of an impressive change in comparison community physicians' practice, the difference in change over time in the intervention community physicians' ordering of annual mammography compared to the change in the comparison community physicians' ordering was significant (P = 0.04). The adjusted odds ratio is nearly 8. We conclude that our in-service continuing medical education program was successful in improving breast cancer screening practices among primary care physicians.