We attempted percutaneous balloon mitral valvuloplasty in 50 patients (27 female and 23 male, age 10-38 years) with rheumatic mitral stenosis. The procedure could be completed in 40 patients. The failures were caused by problems related to transseptal puncture in eight cases and inability to cross the mitral valve in two cases. Immediately after valvuloplasty there was a remarkable reduction in the mean pulmonary artery pressure, left atrial mean pressure, mean diastolic gradient across the mitral valve, and the calculated pulmonary vascular resistance. The calculated mitral valve area increased and the cardiac index increased marginally. Inadequate results with a post valvuloplasty mitral valve area of 0.9 cm2 were seen in only one patient. Repeat hemodynamic evaluation in 25 patients within two weeks of valvuloplasty showed persistent benefit in all except one patient, who showed partial restenosis. Follow-up cardiac catheterization at 3-6 months in 13 patients showed evidence of restenosis (mitral valve area less than 1.0 cm2 and mean diastolic gradient of greater than 10 mmHg) in one patient, while all others maintained hemodynamic benefit. Repeat hemodynamic evaluation at 9-18 months after valvuloplasty in eight patients showed evidence of restenosis in an additional two cases. The patients in our series are young (28 patients less than 20 years), small body surface area (1.35-0.2 m2), and have high left atrial and pulmonary arterial pressures.