Pregnant rats were given a liquid diet containing 5% (w/v) ethanol between gestational days 10 and 21. Cerebella of their offspring were examined at 7 weeks of age. Rats exposed prenatally to ethanol showed a fusion of folia V and VI in the cerebellar vermis. Around the fusion, the cortical laminar structure was disrupted: Purkinje cell dendrites derived from each adjacent folium were tangled, and solitary or clustered ectopic granule cells were in the molecular layer. Some ectopic granule cells surrounded basophilic rosette-like structures. Glial fibrillary acidic protein immunostaining revealed defects in the glia limitans, which is formed by Bergmann glial endfeet on the cerebellar surface. Absence of the glia limitans was observed corresponding to the fusion area. These findings suggested that prenatal exposure to ethanol might impair the formation of the glia limitans in the cerebellum, resulting in the fusion of folia and the disruption of the cortical structure. These malformations may be involved in the delayed motor development and ataxia seen in human fetal alcohol syndrome.