We compared between prosthetic aortic valve size and aortic annulus size in supravalvular aortic cineangiogram in 30` RAO view postoperatively. Retrospectively, supraaortic cineangiogram of 27 patients among the patients underwent aortic valve replacement only or double valve replacement from April, 1986 to January, 1987 was examined and measured the aortic annulus size. In comparing the two values, the cases within 1mm is 22, and the cases within 2mm is 25, correlation coefficient yield r = 0.92. In two cases, the difference between two values is within 3mm We concluded that to prevent the complication from mismatching the prosthetic aortic valve size to patient`s annulus size [e.g. left ventricular failure, hemolysis, limited exercise tolerance], prediction of the prosthetic valve size preoperatively by use of cineangiogram is useful.