Although depressive disorders are common among 20-25% of people with cancer, they are frequently unrecognized. Untreated depression in the presence of comorbid conditions may result in more frequent clinic visits, increased costs, extended hospitalization, and reduced compliance and quality-of-life. Oncology clinicians need not have psychiatric expertise to play a major role in the detection and treatment of depression and in the prevention of suicide. Using early detection and screening tools, the nurse can identify depressed patients and can collaborate in their treatment. Approximately 80-90% of depressed patients are effectively treated with psychotherapy, and/or pharmacologic, or somatic, interventions. Failure to diagnose or reluctance to treat depression among patients with cancer is a common error and can increase morbidity and mortality.