Little is known about the course and outcome of depression in patients with coronary heart disease, despite its prevalence and effect on medical prognosis. A series of 200 patients undergoing diagnostic cardiac catheterization and coronary angiography were administered a psychiatric diagnostic interview. Seventeen percent were diagnosed with a current major depressive episode, and another 17% with a current minor depressive episode. Ninety percent of those patients who consented to follow-up completed the study. Half of the patients with major depression either remained depressed or relapsed within 12 months. Nearly half of the patients with minor depression remitted, but 42% subsequently developed major depression. These results suggest that major depression, if left untreated, is persistent in patients with coronary heart disease. Furthermore, minor depression is nearly as likely to progress to major depression as to remit over the course of the 12 months following diagnostic angiography.