Hydrocephalus associated with a posterior fossacyst and hypoplasia of the cerebellar vermis constitute a traid of Dandy-Walker syndrome. This syndrome was first described by Sutton in 1887. In 1914 Dandy & Blackfan described a case of 13 year old child and thought that these finding were due to atresia of the foramina of Luschka and Magendie. Taggart and Walker, D'Agostino, Giebson and others supported the concept of congenital atresia of the foramina of Luschka and Magendie. However many other authors rejected this concept, and especially Brodal and Hauglie Hanssen pointed out the cerebellar anlage is fused before the foramina normally become patent and thus there was no cause-result relationship between foramina atresia and vermal hypoplasia. They and Gardner thought that this abnormality was the result of preexisting and persistent hydrocephalus and Benda concluded that the entity is a complex developmental abnormaly. There were not a few literature-reported cases in other countries, but in Korea the literature is scarce. We describe an autopsy case of Dandy-Walker syndrome associated with malformations of the brain and additional systemic anomalies, which may be related to acute carbon monoxide poisoning during the early pregnancy period.