OBJECTIVE: Ischemic heart disease is the commonest cause for morbidity and mortality in patients with diabetes mellitus Type II (DMII). Treatment with biguanide drugs has a beneficial effect on lipid profile, decreases insulin resistance, procoagulant activity and body weight. Drugs from the sulphonylurea group cause an increase in insulin secretion, insulin resistance and weight gain. Theoretically, lower rates of cardiovascular events would be expected in patients treated with biguanides. The UKPDS study showed decreased cardiovascular mortality in obese diabetics, but several recent studies reported increased mortality with metformin use. The objective of our study was to compare cardiovascular disease in patients receiving either metformin or sulphonylurea. METHODS: We compared the rates of revascularization procedure in the year 2000 between patients with DMII that were treated either with metformin or glibenclamide. All received the drugs for at least five years. Demographic parameters were similar between the groups. Data were obtained from the computerized database of the largest HMO in the country. RESULTS: 140,757 patients were included in the study. 50.3% were on metformin and 49.7% on glibenclamide. 7601 underwent cardiac revascularization procedures. Of these, 53 % were on glibenclamide and 47% on metformin. The risk of undergoing a revascularization procedure was 1.13 times higher in patients treated with glibenclamide (P < .01). CONCLUSION: The results of our study indicate that patients with DMII treated with metformin have a lower rate of cardiovascular procedures than patients treated with glibenclamide. The use of this group of drugs may decrease the morbidity, mortality and costs in diabetic patients. More studies that include additional end points are needed.