This is a prospective multicenter randomized placebo-controlled double-blind trial assessing the efficacy and safety of rosiglitazone in the prevention of atherosclerosis progression in vein grafts and native coronary arteries of diabetic patients. Stable diabetic patients with previous coronary bypass surgery (≥ 1 year ≤ 10 years) will be screened. After baseline evaluation, all eligible patients will undergo baseline coronary angiogram. IVUS will be performed in a segment length of at least 40 mm in a SVG suitable for IVUS analysis and in a segment length of at least 20 mm in the anastomosed native coronary artery corresponding to the SVG chosen. Following the IVUS procedure, patients will be randomized to either rosiglitazone treatment or to placebo in addition to their standard clinical care. Study drug will be titrated over an 8-week period up to a dose of 8 mg/day (or to maximum tolerated dose). The patients will receive the study drug or the placebo for 50-54 weeks in a double-blind manner. At the beginning and at 2, 4, 6, 8, 10 and 12 months of treatment, patients will be subjected to a set of morphological, physiological and metabolic evaluations. At the final visit (12 months), patients will also be submitted to IVUS and angiography.