Background: Diabetes and insulin resistance are important risk factors for in-stent restenosis even in the era of drug-eluting stents. We investigated in a multicenter registry trial the preventive effect of rosiglitazone on restenosis after coronary stenting with bare metal stents in type II diabetic patients. Methods: We conducted a prospective, case-controlled multicenter trial involving 160 diabetic patients (control group n=75, rosiglitazone group n= 85) undergoing coronary stenting. Rosiglitazone group received 4 mg rosiglitazone daily along with other hypoglycemic agents. Clinical outcomes including major adverse cardiac events (MACE) including death, myocardial infarction, and target lesion revascularization and an angiographic data at 6-month follow-up were analyzed. Results: A fllow-up angiography was performed in 120 patients (64 lesions in control group, 83 lesions in rosiglitazone group) underwent a follow-up angiography. The baseline clinical profile and blood chemistry between two groups were not different. The baseline angiographic data of both groups (rosiglitazone vs. control) were as following: reference diameter 3.15짹0.61 vs. 3.18짹0.48 mm (p=NS), minimal luminal diameter (MLD) 0.74짹0.50 vs. 0.68짹0.43 mm (p=NS), lesion length 18.53 짹6.52 vs. 16.56짹4.85 mm (p=NS). There was no difference in MLD after coronary stenting. At 6-month follow-up, the in-stent restenosis rate was significantly reduced in the rosiglitazone group compare with that of the control group (27.1% vs. 46.3%, P = 0.05). The follow-up MLD (2.29짹0.91 vs. 1.89짹1.03 mm, p=0.031) was larger and late loss was less in rosigltazone group. MACE also occured less frequently at 6 months (12% vs. 22%), however without statistical significance. Conclusions: In diabetic patients undergoing coronary stenting, the rosiglitazone treatment improved the angiographical and clinical outcomes possibly due to pleotrophic property of rosiglitazone.