The effects of ethanol on murine brain development were studied in a model of whole embryo culture and in vivo. Ethanol locally enhances cell death in the primitive neuroepithelium. During neuronal migration, ethanol induces a premature transformation of the radial glial guides into astrocytes. Ethanol also inhibits the late gliogenesis. The resulting postmigratory neocortex displays an abnormal neuronal pattern almost completely deprived of vertical columnization. These glial-neuronal disturbances can explain neuropathological and clinical features of the fetal alcohol syndrome. Our study provides also an experimental tool for the study of cell death in normal and abnormal conditions at early stages of neurogenesis.