BACKGROUND Depression is common but not well diagnosed in primary care medicine. This study examines the influence of depression and its recognition on the physician-patient encounter. METHODS A total of 508 new adult patients were assigned randomly to 105 primary care providers. Self-reported depression was determined by the Beck Depression Inventory (BDI) on entry to the study. Initial visits were videotaped and analyzed using the Davis Observation Code. Chart notes were reviewed for diagnosis of depression. RESULTS Seventy-seven of the 508 study patients (15%) were identified as depressed in chart notes, while 130 patients (26%) had a BDI score > or = 9, indicating moderate to severe depression. Recognition of depression was associated with increased counseling, decreased time conducting physical examination, and an increase in overall visit length. Both elevated BDI scores and physician recognition of depression were associated with decreases in chatting. Failure to recognize depression was associated with increased time taking medical history. CONCLUSIONS Results support the potential value of psychological screening instruments in primary care and provide information for training physicians in the recognition and management of depression. The content of office visits is different when patients are depressed or are diagnosed as depressed.