 One hundred fifty patients who meet the Diagnostic and Statistical Manual of Mental Disorders DSM-IV criteria for a current major depressive episode and who score 15 or higher on the Beck Depression Inventory II with a history of acute MI, unstable angina, or other cardiac event will be enrolled in a randomized, double-blind, placebo-controlled trial of omega-3 augmentation of sertraline. The participants will be randomly assigned to receive either sertraline plus omega-3 or sertraline plus placebo for 10 weeks. At baseline and again after ten weeks, the subjects will complete the following: 1 assessments of depression and psychosocial functioning; 2 24-hour electrocardiogram monitoring for heart rate variability analysis; and 3 blood draws to measure procoagulant and proinflammatory markers, and plasma levels of sertraline and omega-3. If this study shows that omega-3 reduces depression and improves cardiovascular disease markers, there will be a basis for proposing a larger clinical trial to determine whether it can also improve survival after hospitalization for acute MI or unstable angina. 