As emphasized in the recent NIH Consensus Statement on the Diagnosis and Treatment of Depression in Late Life, depression in the elderly is a persistent or recurrent disorder that can result from psychosocial stress or physiological effects of disease and can lead to excess disability, cognitive impairment, increased symptoms from medical illness, physiological effects, increased utilization of health care services, and increased rates of suicide and nonsuicide mortality. Primary prevention can target high-risk groups including those with specific medical illnesses, disabling chronic diseases, widows/widowers, and spousal caregivers. Secondary prevention of recurrences of major depression is possible through maintenance treatment with antidepressant medications. Secondary prevention of behavioral complications such as suicide and alcoholism and of excess disability, morbidity, and utilization of general health services in patients with psychiatric-medical comorbidity can be facilitated by systematic approaches to case identification and treatment for depression in medical patients.