The large incidence of restenosis after coronary angioplasty in diabetic patients renders this procedure less effective than in nondiabetics, and insulin resistance could be a relevant cause of restenosis in such patients. This study assessed insulin resistance and biologic markers of metabolic control in type 2 diabetic patients treated with stented angioplasty. Seventy-four patients were studied prospectively. Biochemical determinations, insulin tolerance test results, and the rate constant for plasma glucose disappearance (K(itt)%) were obtained. The angiographic outcome of angioplasty was assessed by quantitative coronary analysis at baseline and at 6 months in 64 patients (86%). Patients with restenosis had smaller minimum luminal diameters after stenting (2.8 +/- 0.5 vs 3.04 +/- 0.5 mm, p = 0.05), were more often hypertensive (97% vs 79%, p = 0.02) and treated with angiotensin-converting enzyme inhibitors (53% vs 23%, p = 0.02), and had smaller K(itt)% (2.9 +/- 1.6%/min vs 3.7 +/- 1.4%/min, p = 0.04) and larger titers of growth hormone (1.36 +/- 1.5 vs 0.68 +/- 0.6 ng/ml, p = 0.02).