Children with congenital cardiac defects associated with high pulmonary artery pressure may die despite accurate surgery. Postoperative mortality and morbidity have been attributed to acute rises in pulmonary artery pressure and resistance. Acute pulmonary hypertensive crisis is defined as a paroxysmal event in which pulmonary arterial systolic pressure rises to or above systemic levels followed by a rapid fall in systemic pressure and a minor pulmonary hypertensive event is defined as an acute rise in pulmonary arterial pressure to more than 80 % of systemic levels but without a fall in systemic pressure. From Oct. 1988 to Jul. 1989, we experienced 23 patients who showed many pulmonary hypertensive crises after operation in the Department of Thoracic and Cardiovascular Surgery, Seoul National University Childrenulcorner Hospital. Their preoperative PAP/SAPs were 53 to 123 %[mean 93.3%] and diagnoses were VSD[7], TAPVR[5], TGA[4], AVSD[3], MS[1], DORV[1], Truncus arteriosus[1], and AP window[l]. There were 9 deaths among 23 patients and they showed many pulmonary hypertensive crisis episodes during postoperative intensive care, which was managed by sedation, hyperventilation, oxygen, and acidosis correction and which decreased after using tolazoline. In view of our experience, we recommend that pulmonary artery pressure should be monitored in congenital heart defected patient with preoperative pulmonary hypertension to confirm and to manage the pulmonary hypertensive crisis accurately and using tolazoline is helpful in the treatment of pulmonary hypertensive crisis.