Integrated backscatter intravascular ultrasound (IB-IVUS) capable of assessing plaque properties has recently become clinically applicable. We observed short-term atorvastatin-induced changes in coronary arterial plaque properties using IB-IVUS. The patient was a 57-year-old man who underwent coronary angiography when admitted to our hospital for cerebrovascular surgery, and lesions were observed in 2 branches: 99% and 90% stenoses in the proximal anterior descending branch (LAD) and middle region of the circumflex, respectively. Stenting was performed for the LAD on November 4, 2009 and for the circumflex on December 9. Oral atorvastatin administration at 10mg/day was initiated on November 5 because the LDL-cholesterol level was high (160mg/dl). A region about 5mm in length proximal to the stent placed in the LAD was analyzed using IB-IVUS. Atorvastatin lowered the LDL cholesterol level from 160 to 79mg/dl. On IB image analysis, although the period was as short as about 1 month, a marked decrease in the fatty component (44%→26%) and an increase in the fibrous component (53%→66%) were observed in the plaque. It was suggested that atorvastatin changes the tissue properties of coronary arterial plaques from a very early phase. It might be associated with the stabilization of coronary plaque.