Background: It has been suggested that intensive lipid-lowering therapy using statins significantly decreases atheromatous plaque volume. The effect of rosuvastatin on plaque volume in patients with stable coronary artery disease (CAD), including those receiving prior lipid-lowering therapy, was examined in the present study. Methods and Results: A 76-week open-label trial was performed at 37 centers in Japan. Eligible patients began treatment with rosuvastatin 2.5 mg/day, which could be increased at 4-week intervals to ≤20 mg/day. A total of 214 patients underwent intravascular ultrasound (IVUS) at baseline; 126 patients had analyzable IVUS images at the end of the study. The change in the serum low-density lipoprotein-cholesterol level from baseline to end of follow-up was -38.6 ±16.9%, whereas that of high-density lipoprotein-cholesterol was +19.8 ±22.9% (both P<0.0001). Percent change of plaque volume, the primary endpoint, was -5.1 ±14.1% (P<0.0001). Conclusions: Rosuvastatin exerted significant regression of coronary plaque volume in Japanese patients with stable CAD, including those who had previously used other lipid-lowering drugs. Rosuvastatin might be useful in the setting of secondary prevention in patients with stable CAD. (Circ J 2009; 73: 2110-2117)