Objectives: We used serial Intravascular ultrasound (IVUS) to assess the efficacy of rosuvastatin on plaque regression in angina patients with mild to moderate degree of vulnerable plaque burden. Methods: This study was a prospective, randomized, comparative study for lipid lowering therapy using rosuvastatin 20 mg or atorvastatin 40 mg. IVUS was performed during baseline coronary angiography and repeated after 12-month of treatment. Efficacy parameters included changes in atheroma volume and the lipid pool size determined by IVUS. So far, a total of 68 patients were followed (rosuvastatin; 53 lesions in 38 patients vs. atorvastatin; 49 lesions in 30 patients). Results: Low density lipoprotein (LDL)-cholesterol level was reduced from 130짹37 mg/dL to 70짹28 mg/dL in rosuvastatin group (a 46% decrease, p<0.001) and from 117짹35 mg/dL to 76짹24 mg/dL in atorvastatin group (a 35% decrease, p<0.001). Total atheroma and vessel volumes significantly decreased, whereas lumen volume significantly increased from baseline to follow-up in rosuvastatin and atorvastatin groups (���total atheroma volume; -5.25짹8.95 mm3 vs. -3.31짹6.78 mm3, p=0.223, ���vessel volume; -3.79짹12.3 mm3 vs. -3.20짹9.01 mm3, p=0.784, ���lumen volume; 1.45짹8.63 mm3 vs. 0.70짹5.54 mm3, p=0.605, ���percent atheroma volume; -0.65짹1.78% vs. -0.29짹1.81%, p=0.314, respectively). Lipid pool size decreased more significantly in rosuvastatin group compared with atorvastatin group (���; -0.80짹0.36 mm2 vs. -0.59짹0.29 mm2, p=0.044). Follow-up LDL-cholesterol level correlated with change in total atheroma volume (r=0.327, p=0.001), change in percent atheroma volume (r=0.292, p=0.003), and change in lipid pool size (r=0.485, p=0.001). Conclusions: Both rosuvastatin 20 mg and atorvastatin 40 mg could contribute to the regression of lipid-rich plaque, and LDL-cholesterol lowering is important in the regression and stabilization of the vulnerable coronary plaque.