Background: The quality of care for asthma remains suboptimal. Compliance with guidelines remains low, but improved adherence to guidelines may increase the quality of care. but. We conducted a trial to determine whether group Self-Assessment Module (SAM) activities led by a facilitator and conducted as part of Maintenance of Certification for Family Physicians (MC-FP) would increase knowledge of and adherence to asthma guidelines. Methods: Participating physicians completed audits of the charts of patients with asthma before and 6 months after a group SAM. Surveys of physicians' knowledge of asthma guidelines were administered immediately before, immediately after, and 6 months after the group SAM. We tested for differences in knowledge of and adherence to guidelines before and after the SAM using u03c7(2) and t tests. Results: Thirty-eight physicians in Virginia completed the SAM and had complete data. Participants completed more MC-FP activities than other physicians but were comparable in other characteristics. Except for prescribing controller medications for persistent asthma, all other quality measures significantly improved 6 months after the group SAM. Diagnosis by severity improved from 48.3% to 80.2%, and the use of action plans increased from 8.1% to 54.1%. Physicians' knowledge of guidelines improved immediately after the SAM and was sustained at 6 months. Increased knowledge translated into clinical skills: 30% of participants reported comfort with assessing control after the SAM, which increased to 97.5% 6 months after the SAM. Conclusions: Group SAMs may be an effective method to increase physicians' knowledge of and adherence to clinical guidelines.