The Institute of Medicine's reports and discussions on quality of medical care have focused on a systems-based approach to quality improvement. Our objective is to summarize evidence and theory about the role of a physician's current board certification status in quality improvement. The first body of evidence includes the validity of board certification demonstrated by the testing process, the relationship of examination scores with other measures of physician competence, and the relationship between certification status and clinical outcomes. The second body of evidence involves the adaptation of error prevention theory to medical care. Patient safety is enhanced when problem-solving uses readily accessed habits of behavior, the same behavior necessary to achieve board certification. The third body of evidence, obtained through a Gallup poll, demonstrates that certification and maintenance of certification are highly valued by the public. The majority of respondents thought it important for physicians to be reevaluated on their qualifications every few years and that physicians should do more to demonstrate ongoing competence than is currently required by the profession. We conclude that a physician's current certification status should be among the evidence-based measures used in the quality movement.