Objectives. This study was designed to assess the left ventricular peak systolic pressure/end-systolic volume (PSP/ESV) ratio in predicting symptomatic improvement with valve replacement in patients with aortic regurgitation and enlarged left ventricular volume. Background. Patients with aortic regurgitation and a left ventricular end systolic volume less than or equal to 60 ml/m(2) show symptomatic improvement with valve replacement, whereas the response of those with an enlarged end systolic volume >60 ml/m(2) is mixed. Most benefit, but some do not. Valve replacement appears to help those whose end-systolic volume is enlarged because of excessive left ventricular afterload but appears to have little or no effect in those whose end-systolic volume is enlarged because of depressed left ventricular contractility. Methods. We studied 27 patients (21 men and 6 women aged 18 to 72 years) with moderate or severe aortic regurgitation, no other cardiovascular abnormalities and left ventricular end-systolic volume >60 ml/m(2). In this group we assessed the ability of preoperative variables routinely measured at cardiac catheterization to predict symptomatic improvement with valve replacement. Results. Of the 27 subjects, 1 (4%) died 51 days postoperatively. Six months postoperatively, symptoms had lessened in 17 patients (63%), were unchanged in 8 (29%) and had worsened in 1 (4%). By multivariate analysis, the PSP/ESV ratio was the strongest predictor of both functional class 6 months postoperatively (p = 0.026) and change in functional class from before operation to 6 months postoperatively (p = 0.033). By 6 months after valve replacement, all patients with a ratio greater than or equal to 1.72 mm Hg/ml per m(2) were in functional class I or II; in contrast, of those with a ratio <1.72 mm Hg/ml per m(2), 31% were in functional class III, and 1 (8%) had died. Conclusions. The PSP/ESV ratio may help to predict which patients with aortic regurgitation and enlarged left ventricular end-systolic volume will have symptomatic improvement with valve replacement.