The steadily increasing number of operations performed on the heart has given rise to occasional complications involving the nervous system, and this has been interested to cardiac surgeons and neurologists. This survey has been carried out on all Gases submitted to open heart surgery at Seoul National University Hospital during 1982 to determine which operative features were associated with the occurrence of neurological damage. 514 subjects were studied and neurological damage was noted in twenty-five patients [4.9%]. Eight of these 25 patients died in the postoperative period, but neurological damage contributed to the fatal outcome in six cases. Remaining seventeen patients were discharged without problems except one Cortical blindness and one hemiplegic patients who were survived without other problems . A number of features were found to be related to the development of neurological damage, which were age, duration of perfusion, nature of operation, cardiac rhythm and presence of the thrombi or calcification and hypothermic arrest. But many unknown etiological factors are remained out of our sight. A significant increase in the incidence of neurological damage was shown in older age group [13.3% in over 40 year of age], and also the duration of the bypass was associated with subsequent neurological injury especially more than 120 minutes [11.6%]. The presence of atrial fibrillation with intracardiac thrombi or calcification was also a contributing factor to developing neurological complication [16.7%]. These factors were regarded to influence the postoperative neurological complications and more effective method for prevention of these neurologic complication should be studied. [KTCS 1983;1:97-101]