144 surgical patients with isolated aortic valve disease were reviewed to determine the incidence and the mechanism of pulmonary hypertension (PH). The hemodynamic data revealed PH (pulmonary artery systolic pressure of 40 mmHg or more) in 18 patients (12.6%). There was a positive correlation between left ventricular end-diastolic pressure (LVEDP) and pulmonary artery pressure. After operation the pulmonary artery pressure normalized in all cases but 2 patients in early post-operative period. In patients with aortic stenosis with PH, LVEDP/LVEDVI ratio was higher than that of patients without PH, which showed left ventricular diastolic dysfunction. In patients with aortic regurgitation with PH, the cause of elevated LVEDP was not only severe long-standing regurgitation with ventricular dysfunction, but also the imbalancement of compensation by dilated ventricle with preserved left ventricular function.