The aim of this study was to evaluate the effect of diabetes mellitus on the prognosis of patients with chronic ischemic heart disease. The multicenter prospective cohort study involved 1108 outpatients with ischemic heart disease whose clinical characteristics were recorded by 69 primary care physicians. Morbidity and mortality were recorded during a mean follow-up period of 6.9 months. Overall, 29% of patients were diabetic; they were older than non-diabetics, presented with more risk factors, had poorer blood pressure control, and had more comorbid conditions. In addition, diabetics were more likely to be prescribed renin-angiotensin system blockers, calcium channel blockers, diuretics and lipid-lowering drugs. Cardiovascular mortality and hospitalization rates were higher in diabetics. On multivariate analysis, diabetes was found to be an independent predictor of a cardiovascular event (hazard ratio=1.81; 95% confidence interval, 1.17-2.82). Prognosis in chronic ischemic heart disease is relatively good, although it is worse in diabetics, which means that treatment and disease controls targets must be more rigorously applied in these patients.