At the Dept. of Thoracic and Cardiovascular Surgery of Pusan National University Hospital, postoperative cardiac catheterizations were performed in 12 patients of ventricular septal defect with severe pulmonary hypertension [Pp/Ps>0.75], who were operated during the period from July 1981 to Dec. 1986. The mean age of the patients preoperatively was 12.4 [range: 4-18] year-old and the mean follow-up duration was 25.8 [range: 8-53] month per patient. In comparison with the preoperative data, the systolic pulmonary artery pressure [SPAP] was decreased from 103.6*18.4 to 70.4*35.9 mmHg [p<0.01] and the Pp/Ps was decreased from 0.89*0.10 to 0.58*0.27 [p<0.01]. But the Rp/Rs and Rp were not meaningfully changed, from 0.31*0.16 and 7.6*0.4 unit to 0.41*0.32 and 8.0*6.6 unit, respectively. The preoperative Qp/Qs was bellow 2.0[mean: 1.6] in 3 out of 4 cases whose postoperative Rp/Rs and Rp were above 0.75 and 15 unit, respectively. On the contrary, the preoperative Qp/Qs was above 2.0 [mean: 3.5] in all of the 8 cases, whose postoperative Rp/Rs and Rp were below 0.50 and 10 unit, respectively.