From a total group of 189 children with a ventricular septal defect operated in 1978-1985 at the Cardiosurgical and Transplantation Department in Brno the authors followed up 60 patients with pulmonary hypertension. In addition to catheterization and echocardiographic examination, they made in 28 patients (46%) a preoperative pulmonary biopsy. In the majority of children before and after operation by catheterization the pulmonary tension Rp/Rs was measured and in some also pulmonary vascular resistance. During the echocardiographic examination attention was focused on the possibility to as the pulmonary tension by pulsed Doppler and continuous technique, on the detection of left-to-right shunt, pulmonary or tricuspid insufficiency. Of 60 patients 5 children (8.3%) died soon after operation, one patient died six years after operation. Long-term postoperative follow up made is possible to define more accurate indication criteria for operation as well as for pulmonary biopsy.