Acute carbon monoxide poisoning has frequently occurred in Korean, because of the coal briquette being widelyused as fuel in Korean residences. Carbon monoxide poisoning has been extensively studies, but it has beensparsely reported that pulmonary edema may develop in acute CO poisoning. We have noticed nine cases of pulmonaryedema in acute CO poisoning last year. Other possible causes of pulmonary edema could be excluded in all cases butone. The purpose of this paper is to describe nine cases of pulmonary edema complicated in acute CO poisoning anddiscuss the pathogenesis and the prognosis.