Prior studies in our laboratory have shown that exposure of cultured fetal rat hepatocytes to ethanol (E) blocks epidermal growth factor-dependent replication and that this is paralleled by cell membrane damage, mitochondrial dysfunction, membrane lipid peroxidation (LP), and enhanced generation of reactive oxygen species. These measures of E-mediated oxidative stress (OS) were mitigated by treatment with antioxidants, and cell replication could be normalized by maintaining cell glutathione (GSH) pools. We have now extended these studies to an in vivo model. Rats were administered E (4 g/kg, po) at 12-hr intervals on days 17 and 18 of gestation and killed on day 19,1 hr following a final dose of E (a total of 5 doses). Fetal and maternal brain and liver were assayed for signs of OS. The 2-day in utero E exposure increased membrane LP in fetal brain as evidenced by increased malondialdehyde (MDA) levels from 1.76 ± 0.12 se (nMol/mg protein) to 2.00 ± 0.08 (p < 0.05) and conjugated dienes from 0.230 ± 0.006 se (OD233/mg lipid) to 0.282 ± 0.006 (p < 0.05). In fetal liver, MDA levels increased from 2.39 ± 0.08 se (nMol/mg protein) to 2.87 ± 0.08 (p < 0.05), whereas dienes differed significantly only between ad libitum controls and the E and pair-fed control groups (p < 0.05). E decreased GSH levels in fetal brain by 19%, from 19.88 ± 0.72 to 16.13 ± 1.06 (nMol/mg protein) (p < 0.05). A10% decrease in GSH was seen in fetal liver (p < 0.05). GSH in maternal brain was decreased by 44% from 47.29 ± 3.38 to 26.60 ± 2.29 (p < 0.05). Other E-related increases in these OS measures were not observed in maternal organs. E did not decrease α-tocopherol levels in fetal and maternal brain or in fetal liver (p < 0.05), whereas maternal liver α-tocopherol content was reduced by 31% (p < 0.05) by E treatment. It is concluded that maternal E consumption can induce an OS in fetal tissues that may contribute to the fetotoxic effects of E.