Objective This prospective study was performed to assess the effects of 1 year of angiotensin-converting enzyme inhibition with captopril in 20 children (mean age 14.3 ± 2.3 years) with asymptomatic chronic aortic regurgitation. Methods and Results At 12 months patients receiving captopril had a significant reduction in left ventricular end-diastolic and end-systolic dimensions (57 ± 9.3 vs 51 ± 9.5 mm, p < 0.001; 35.4 ± 6.1 vs 32 ± 6.8 mm, p < 0.001), end-diastolic and end-systolic volume indexes (111 ± 36 vs 94 ± 29 ml/m², p < 0.001; 35 ± 13 vs 30 ± 12 ml/m², p < 0.001, respectively), and mass index (138 ± 37 vs 109 ± 32 gm/m², p < 0.0001) determined by two-dimensional echocardiography. Meridian (p < 0.01) and circumferential (p < 0.0001) wall stresses also decreased significantly with therapy. Significant reduction (27.8%, p < 0.0001) was achieved in regurgitant fraction with captopril. Conclusions These data show that the long-term therapy with angiotensin-converting enzyme inhibitors is able to reverse left ventricular dilation and hypertrophy and suggest that such therapy has the potential to favorably influence the natural history of the disease in children. (Am Heart J 1998;135:598-603.)