Physicians diagnosed depression in 4.5 percent (59/1,321) of all patient encounters in this study conducted in a university based family medicine residency program. A subset of residents permitted the investigators to interview those patients who were diagnosed as depressed or who were judged to be at high risk for a missed diagnosis of depression. Of the six patients whom the residents diagnosed as depressed and who agreed to be interviewed, two did not meet the criteria for depression but in neither case was this discrepancy judged clinically significant. Of the 24 patients at high risk for a missed diagnosis who agreed to be interviewed, four met the diagnostic criteria and three of these four missed diagnoses were judged as possibly of clinical significance. While the physicians in this study diagnosed depression more frequently than in previous similar studies, this does not appear to represent over-diagnosis, although the small number of patients interviewed requires that interpretations be made cautiously. The authors suggest that if a primary care physician diagnoses depression in less than 2 percent of patient encounters, he or she should consider the possibility of missed diagnoses.