Depressive disorders are common, chronic, and costly. Lifetime prevalence levels from community-based surveys range from 4.9% to 17.1%. In primary care settings, the prevalence of major depression is 6% to 8%. Longitudinal studies suggest that about 80% of individuals experiencing a major depressive episode will have at least 1 more episode during their lifetime, with the rate of recurrence even higher if minor or sub-threshold episodes are included. Approximately 12% of patients who experience depression will have a chronic, unremitting course. The substantial public health and economic significance of this chronic illness is reflected by the considerable utilization of health care visits and tremendous monetary costs: $43 billion (1990 dollars) annually, with $17 billion of that resulting from lost work days. The burden of suffering from depression is substantial. Suicide, the most severe of depressive sequelae, has a rate of approximately 3.5% among all cases with major depression, a risk that increases to approximately 15% in people who have required psychiatric hospitalization. The specific risk for suicide associated with depressive disorders is elevated 12- to 20-fold compared to the general population. The World Health Organization (WHO) identified major depression as the fourth leading cause of worldwide disease burden in 1990, causing more disability than either ischemic heart disease or cerebrovascular disease. Its associated morbidity is expected to increase; unipolar depressive illness is projected to be the second leading cause of disability worldwide in 2020. Furthermore, depression appears to contribute to increased morbidity and mortality from other medical disorders, such as cardiovascular disease. Both the chronicity and recurrence of depressive illness play a large role in depression's heavy disease burden. The more severe a depression becomes and the longer it lasts, the greater the likelihood that the depression will become chronic. Consequently, early effective identification and management of depressive illness will not only decrease the substantial morbidity associated with the current episode but may also decrease the likelihood that the illness will become chronic, with its additional associated morbidity. Key questions addressed include: 1. What is the accuracy of screening instruments for depression in primary care populations? 2. Is treatment of depression in primary care patients (with pharmacologic therapy, psychotherapy, combinations of the 2, or educational interventions) effective in improving outcomes? 3. Is screening more effective than usual care in identifying patients with depression, facilitating treatment of patients with depression, and improving outcomes?