The purpose of this study was to determine the threshold at which depression becomes important for the daily functioning of patients with heart disease. Data from a 1-year prospective cohort study of health maintenance organization patients undergoing coronary angiography for coronary heart disease were analyzed for differences in a standardized composite measure of functioning. Patients with major depression (N = 19) and patients with minor depression (N = 28) were significantly more functionally impaired at baseline and at 1-year follow-up than those with no depression (N = 110). The major and minor depression groups did not differ significantly. The significance of the depression group differences was reduced, but not eliminated, when controlling for differences in reported heart symptoms.