A 4(1/2)-month-old patient who underwent mitral valve replacement for congenital mitral stenosis using a pulmonary autograft is reported. Failure of the autograft resulted in pulmonary hypertension, leading to pulmonary regurgitation in the reconstructed right ventricular outflow tract, then tricuspid regurgitation, refractory right heart failure, and death. Caution should be exercised in applying this procedure with children, particularly those at risk for pulmonary hypertension.