The possibility of free radicals effects in ethanol-induced teratogenesis was investigated by determining the production of reactive oxygen species (ROS) in the neonatal rat brain. Ethanol 33% was administered daily, by i.p. injection from day 8 of pregnancy to day 6-8 p.n. The presence of the lipid peroxidation process (indicating ROS formation) was determined by using a qualitative and quantitative analysis of malondialdehyde (MDA). An important increase of MDA was found suggesting the involvement of ROS in the pathogenetic mechanism of alcohol embryo- and fetopathy.