Neurologic complications after open-heart surgery are not only relatively common but also often fatal. In order to know the clinical characteristics and causative risk factors, we carried out the retrospective study on 655 patients who had been admitted and undergone OHS at Seoul National University Children's Hospital during 2-year period from July 1990 to June 1992. The results were as follows; 1) The incidence of neurologic complications after OHS was 4.7% (31 cases) of the total 655 cases. 2) In the viewpoint of the pre-op diagnosis, neurologic complications developed in 20 cases (7.8%) among cyanotic congenital heart disease and in 11 cases (2.9%J among acyanotic CHD. 3) In the viewpoint of the type of operation, the incidence of neurologic complications was 33.3% in Jatene procedure and 12.1% in Fontan procedure. 4) Compared with the group who didn't develp neurologic complications (624 cases), cardiopulmonary bypass time, aorta cross clamp time, and total arrest time were longer and the degree of hypothermia was lower in the group who had neurologic complications (31 cases), which are statistically significant each other(p<0.01). 5) In 25 cases (80.6%), neurologic complications occurred within 72 hours after OHS. 6) Clinical manifestations of neurologic complications were seizures (26 cases, 84%), consciousness change (13 cases, 42%), hemiplegia (1 case), and decreased muscle tone (1 case). 7) Of the 31 cases, 16 cases showed more than one abnormal finding among EEG, Brain CT, or Brain MRI. 8) The possible etiologies of neurologic complications were diffuse hypoxic ischemic encephalopathy (16 cases, 51.6%), focal or multiple ischemic stoke that was thought to be due to microembolisms (3 cases, 9.7%), electrolyte or acid-base imbalance (8 cases, 25.8%), and the remainders were unknown (4 cases. 12.9%) 9) In the course of neurologic complications, 11 cases (35.5%) expired, 14 cases(45.2%) recovered at discharge, 3 cases (9.7%) were controlled at discharge, and 2 cases (6.5%) had long-term sequela(one spastic quadriplegia and one hemiparesis). 10) The cause of death among mortality cases were mainly due to brain damage (7 cases), while 4 cases had other direct causes such as heart failure, respiratory failure, or sepsis.