The upstroke time ratio has been studied in 15 normal controls and in 31 patients with pure aortic regurgitation and varying stages of myocardial involvement. The upstroke time ratio results were as follows: 15 normal subjects, 0.50 to 0.70; 31 patients with rheumatic aortic valvular insufficiency, of whom 9 had cardiac decompensation, 0.50 to 0.80; and 22 with no evidence of myocardial failure, 0.31 to 0.50. These patients were graded from 0 to IV, depending upon the degree of aortic regurgitation by the Braunwald method. Those with lower ratio had grade III and IV regurgitant index and were found to have good myocardial reserve. Others with grade III and IV and elevated ratio were classified as having poor myocardial reserve, and should be high surgical risks if open heart surgery is performed. The upstroke time ratio is an indirect measurement of aortic valvular regurgitation and is a useful index in evaluating secondary myocardial involvement.