Prevention of Suicide in Primary Care Elderly: Collaborative Trial (PROSPECT) aims to prevent suicide among older primary care patients by reducing suicidal ideation and depression. It also aims to reduce their risk of death. The intervention components are (1) recognition of depression and suicidal ideation by primary care physicians, (2) application of a treatment algorithm for geriatric depression in the primary care setting, and (3) treatment management by health specialists (e.g., nurses, social workers, psychologists). The treatment algorithm assists primary care physicians in making appropriate care choices during the acute, continuation, and maintenance phases of treatment. Health specialists collaborate with physicians to monitor patients and encourage patient adherence to recommended treatments. Patients are treated and monitored for 24 months.