This 11-year-old girl with Down's syndrome had severe aortic valvular stenosis with a pressure gradient of 95 mmHg. Balloon valvotomy failed to reduce the pressure gradient. Surgical correction was performed. The aortic valve was bicuspid with fibrotic change and the anulus was about 10 mm in diameter. The aortic valve was resected, and the anulus was enlarged by a combination of the Nicks and Konno procedures. Then, a St. Jude 19 mm mechanical prosthesis was implanted, and the right ventricular outflow tract was repaired with a baked woven Dacron patch. The postoperative course was very uneventful. She was discharged in good condition on the 10th postoperative day. A combination of the Nicks and Konno procedures is recommended to correct very small aortic anuli requiring extensive enlargement of the aortic root.