Background : The risk of cardiovascular diseases is two to four times higher in diabetic patients. Aim: To study the severity of coronary disease and survival of patients with diabetes mellitus, compared to matched controls without diabetes. Patients and methods: A retrospective review of all coronary angiographies performed at a private hospital. All diabetic patients with coronary lesions over 50% were considered as the index group. Non diabetic patients with coronary artery lesions over 50% and with similar demographic features and risk factors to the diabetic patients group, were studied as controls. A follow up was done reviewing clinical records and by telephone interviews. Mortality was obtained reviewing death certificates. Results: Seventy seven diabetic patients (48 male, mean age 61±10 years and 129 non diabetic subjets (87 males, eman age 61±10 years) were studied. Mean follow up in diabetic and non diabetic patients was 1,270 and 1,340 days respectively. Diabetic patients had a higher frequency of multiple vessel disease than their non diabetic counterparts (69 and 52% respectively, p <0.003). Ejection fraction was 61 and 65% in diabetics and non diabetics. General mortality was 15.5 and 2.3% in diabetics and non diabetic respectively (p <0.01). Cardiovascular mortality was 9.1 and 0.8% in diabetics and non diabetics respectively (p 0.002). Conclusions: Diabetic patients with coronary artery disease have a lower survival and more extensive coronary artery lesions than non diabetic patients with similar age, sex and overall coronary risk (Rev Méd Chile 2004; 132: 331-6).