Exposure to ethanol during fetal development reduces the astroglial-specific marker glial fibrillary acidic protein (GFAP) and its mRNA levels in brains of fetal rats and in radial glia in primary culture, affecting the proliferation and differentiation of astrocytes. The objectives of this study were to evaluate the possible effect of ethanol on GFAP mRNA levels in astrocytes and to investigate the molecular mechanism(s) involved in ethanol-induced changes in GFAP expression by analyzing the GFAP transcription rate, GFAP mRNA stability, and GFAP DNA methylation. We show here that prenatal exposure to ethanol reduces significantly GFAP immunoreactivity and its mRNA levels in both astrocytes in primary culture and brains of pups from alcohol-fed mothers. Runoff experiments from nuclei of astrocytes indicate that ethanol exposure decreases GFAP transcription rate significantly and reduces GFAP mRNA stability slightly. DNA methylation analysis indicates that prenatal ethanol exposure induces a hypermethylated state of the GFAP DNA in fetal brains. Methylation-mediated repression of GFAP transcription could be a mechanism involved in ethanolinduced reduction of GFAP expression. Ethanol-induced alterations in GFAP expression and astroglial development may underlie the CNS dysfunctions observed after prenatal alcohol exposure. Key Words: Prenatal ethanol exposure-Brain development-Astrocytes in cultureGlial fibrillary acidic protein-Vimentin-mRNA-Transcription-Runoff-mRNA stability-Methylation-Fetal alcohol syndrome.