Between 1972 and 1987, 43 patients underwent isolated mitral valve replacement with mean pulmonary arterial pressures greater than 50 mmHg. The valve disease was stenosis in 13 cases, regurgitation in 15 cases and mixed mitral valve disease in 15 cases. Forty-one patients (95 %) had invalidating cardiac failure (Stages III and IV of the NYHA Classification). The hospital mortality was 2.3%. Thirteen patients died during follow-up, 8 of cardiac failure, 3 of sudden death and 2 died of non-cardiac causes. The 8 year actuarial survival was 82 +/- 7% with an average postoperative follow-up of 96 +/- 41 months. No patients were lost to follow-up. Eighty six per cent of survivors (25/29) are asymptomatic or paucisymptomatic. Doppler studies were performed in 22 patients, showing normal prosthetic function in 18 cases and an obstructive prosthesis in 4 cases. Seventeen patients had tricuspid regurgitation showing normal pulmonary artery systolic pressures in 9 cases and less than 55 mmHg in 5 cases. On average, systolic pulmonary artery pressure fell from 88 +/- 11 mmHg before to 33 +/- 9 mmHg after surgery (p = 0.01). These results show that severe pulmonary hypertension is not prohibitive for mitral valve replacement. The long-term results are good with functional improvement and reduction of pulmonary hypertension.