A key component of Maintenance of Certification (MOC) for family and internal medicine physicians is the requirement to pass a periodic examination of medical knowledge. Little is known about the effects of preparing for MOC exams on knowledge and practice.To understand how MOC exam preparation can affect knowledge and practice.Qualitative, semi-structured interviews, 45-60 min each, conducted by telephone at participants' convenience.A total of 80 primary care physicians from the American Board of Family Medicine (ABFM) and the American Board of Internal Medicine (ABIM) who had recently taken an MOC exam; the sample purposefully selected to represent diversity of experiences with MOC exams and range of opinions about MOC, as well as diversity of participant backgrounds-gender, practice type, etc. APPROACH: Close analysis of physicians' accounts of what they learned when preparing for an MOC exam and how this knowledge affected their practice.Sixty-seven of 80 physicians stated they gained knowledge relevant to their practice. Sixty-three gave concrete examples of how this affected their practice, including direct changes to patient care (e.g., improved diagnosis or prescribing and reduced unnecessary testing) or less direct changes (e.g., improved ability to co-manage with other providers or communicate with patients). Physicians also described sharing what they learned with others, including peers and trainees.Interviews could have been affected by recall and/or social desirability bias, as well as researchers' role as board staff. Although we followed a recruitment protocol designed to mitigate recruitment acceptance bias, our findings may not be generalizable to wider groups of physicians.Most physicians from two primary care specialties interviewed reported ways in which studying for an MOC exam resulted in acquiring knowledge that was both relevant and beneficial to their patient care.