During the last 15 years, isolated aortic valve replacement was performed in 122 patients, 12 of whom had severe elevated pulmonary systolic pressure (PAS) of 50mmHg or over. A comparative study of preoperative and postoperative data was done between two groups; group I (n=12), with a pulmonary systolic pressure 50mmHg or over, and group II, with a value of under 50 mmHg (n=45). On preoperative evaluation, cardiomegaly and constrictive pulmonary dysfunction were found in group I and also PAWP, mean pressure of PA, PAS, LVEDP and RVEDP were of a higher value in group I than group II. The LVEDP was high in group I and correlated well with PAS preoperatively, suggesting that pulmonary hypertension was a consequence of severe LV dysfunction. There was no difference in the operative mortality and postoperative complication between these two groups. CTR, PAWP, mPA and PAS decreased to within the normal range postoperatively. It was concluded that pulmonary hypertension does not adversely effect the operative mortality and postoperaive complications of AVR, and the cause of the elevated pulmonary pressure was thought to be due to the impaired LV function.