This article reviews the epidemiology of comorbid coronary artery disease and unipolar depression. Both major depression and subsyndromal depressive symptoms will be considered; unless otherwise specified, the term depression will be used to designate all depressive states, including major depressive disorder, minor depression, dysthymia, and other subsyndromal forms of depression. While 17% to 27% of patients with coronary artery disease have major depression, a significantly larger percentage has subsyndromal symptoms of depression. Patients with coronary artery disease and depression have a twofold to threefold increased risk of future cardiac events compared to patients without depression, independent of baseline cardiac dysfunction. The relative risk for the development of coronary artery disease conferred by depression in patients initially free of clinical cardiac disease is approximately 1.5, independent of other known risk factors for coronary disease. In the discussion, special attention will be paid to the interactions of both gender and age with depression and coronary artery disease risk. Scrutiny of the role of confounding risk factors is presented, such as global burden of comorbid medical illness and modification of traditional risk factors, which may, in part, mediate the effect of depression on coronary artery disease.