100 hospitals will participate in the PPAR study. Patients with DM who have history of prior myocardial infarction are randomly allocated to receive pioglitazone or (1)instructs weight reduction, appropriate diet, regular exercise and/or (2)prescribes sulfonylurea agents. The number of patients to be recruited is 3000 and this study will continue at least 2 years. The primary end-points are (1) cardiovascular mortality and (2) hospitalization for cardiovascular events. Effects in suppression of new diabetes development also will be evaluated.