To see the change of pulmonary arterial pressure after mitral valve replacement, postoperative cardiac catheterization and echocardiographies were performed in 12 patients of mitral valvular disease with pulmonary hypertension[systolic pulmonary arterial pressure>50 mm Hg]. The mean follow-up duration was 35.4[range: 15-47] months per patient. The following results were obtained. 1] Preoperative systolic pulmonary arterial pressure value of 66.17ulcorner10.73mmHg decreased significantly to 29.17ulcorner6.86mmHg postoperatively[p<0.01]. 2] Preoperative Pp/Ps value of 0.67ulcorner0.13 decreased significantly to 0.28ulcorner0.06 postoperatively[p<0.01]. 3] Preoperative PAWP value of 29.00ulcorner4.02mmHg decreased significantly to 9.92ulcorner4.27 mmHg postoperatively[p<0.01]. 4] Preoperative LAD value of 5.58ulcorner1.20cm decreased significantly to 4.37ulcorner0.67cm postoperatively [p<0.01]. In conclusion, pulmonary arterial hypertension secondary to mitral valvular disease could be reduced to normal range after successful mitral valve replacement.