Depression is a common psychiatric disorder in children, adolescents, adults, and the elderly. Primary care physicians, not mental health professionals, treat the majority of patients with symptoms of depression. Persons who are depressed have feelings of sadness, loneliness, irritability, worthlessness, hopelessness, agitation, and guilt that may be accompanied by an array of physical symptoms. A diagnosis of major depression requires that symptoms be present for two weeks or longer. Identifying patients with depression can be difficult in busy primary care settings where time is limited, but certain depression screening measures may help physicians diagnose the disorder. Patients who score above the predetermined cut-off levels on the screening measures should be interviewed more specifically for a diagnosis of a depressive disorder and treated within the primary care physician's scope of practice or referred to a mental health subspecialist as clinically indicated. Targeted screening in high-risk patients such as those with chronic diseases, pain, unexplained symptoms, stressful home environments, or social isolation, and those who are postnatal or elderly may provide an alternative approach to identifying patients with depression.