Although continuity of care occupies a central position in the definition of primary care and is invoked as having evident importance in practice, research on the value of continuity has produced confusing and conflicting results. These results may be due to a lack of clarity in the definition of continuity of care. In this paper, the authors suggest that continuity includes three elements--cognitive, management, and relationship. Exploration of each of the elements expands the understanding of continuity in medical practice. Continuity of care can be evaluated in both undergraduate and residency programs by the application of criteria offered in this paper.