Childhood and adolescent depression is probably more common in the primary care setting than most physicians realize. Because depression can result in suicide, it must be differentially diagnosed from the more common complaints seen in pediatric and adolescent patients. The cause of depression is usually multifactorial and may include psychodynamic, cognitive, behavioral, life stress/socioenvironmental, biologic/biochemical, and genetic components. Depending on the patient's age, depression can present as mood disturbances, and eating and sleeping disturbances, as well as somatic complaints. With no laboratory tests currently available to diagnose depression, physicians must rely on the history and physical examination as the best diagnostic tool. To aid family practitioners, the authors present criteria for diagnosing depression from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition along with treatment that includes psychotherapy and pharmacotherapy for the best possible outcome.