We reoperated for diffuse supravalvular aortic stenosis using a modified technique of patch plasty described by Brom. A 36-year-old woman admitted to our hospital with a peak systolic pressure gradient of 92 mmHg across the ascending aorta had previously undergone Doty's operation at another hospital. Aortography showed an ascending aorta diffusely stenotic from the sinotubular junction to the aortic arch. We transected the ascending aorta just above the stenotic portion and incised the proximal wall to the sinus of Valsalva. Three patches were sewn to each sinus to expand them and the ascending aorta. The pressure gradient decreased postoperatively to 11 mmHg, and we conclude that this technique sufficiently relieves diffuse supravalvular aortic stenosis.