Background In addition to the hypoglycemic effect, rosigitazone was known to have a several vascular protective effects in patients with type 2 diabetes mellitus through the activation of peroxisome proliferators-activated receptor-款 (PPAR-款). Objective This study evaluated the effects of Rosiglitazone on coronary atherosclerosis as determined by IVUS imaging in type 2 diabetic patients Methods We conducted a prospective, randomized, case-conrolled trial involving 10 patients with diabetes mellius with coronary artery disease who were randomly assigned to either the control (n=5) or rosiglitazone group (n=5). In all patients, simvastatin was administered 20mg daily. The rosiglitazone group was treated with 4mg rosiglitazone daily, combined with conventional antidiabetic therapy for 12 months. Qunatitative coronary angiography (QCA) and IVUS analysis were performed in the non-target vessel at study entry and again 12 month follow-up. The percent atheroma volume (PAV) was calculated by every cross-section images spaced exactly 1.0mm apart from the selected distal branch site as the beginning point of analysis and compared PAV between initial and after 12 months in each group.Results The baseline and follow-up glucose, HgA1c, hs-CRP and lipid concentrations were not different between two groups. In both groups, there were no statistical differences in minimal luminal diameter (MLD) and diameter stenosis (DS) before and after 12 months. The mean vessel length in which IVUS was performed was 30.1짹6.8mm. The mean change in PAV for the entire vessel was -4.4짹1.6% in the rosiglitazone group (p<0.05; 95% CI, -27.2 to -1.63%) and 1.5짹4.0% in the control group (p=0.47). the mean change in atheroma volume in the most diseased 10mm subsegment was – 5.3짹3.2mm3 in the rosiglitazone group (p<0.05; 95% CI, -10.32 to -0.27 mm3) and 0.1짹7.0 mm3 in the control group(p=0.982).Conclusion On IVUS studies, 12-month treatment with 4mg rosiglitazone significantly reduced atheroma volume in patients with type 2 diabetes mellitus. These results suggest that the activation of PPAR-款 plays a role in the reduction of atheroma volume.