The effects of acute ethanol treatment and dietary folate deficiency on maternal-fetal folate transfer were studied to asses the hypothesis that the potentiation of ethanol's toxic effect on the fetus during ongoing folate deficiency was due to the impairment of folate transfer. Sprague-Dawley rats were fed either a folate-deficient diet (0.2 mg/kg) or a folate-sufficient diet (2 mg/kg) for an average of 11 weeks before pregnancy and continued until gestation day 11 when they were sacrificed. On gestation day 11, pregnant rats were treated with either ethanol (2.5 g/kg body weight) or isocaloric sucrose (control) followed by an intravenous administration of 3H-folate (2 muCi/100 g body weight) at 120 minutes. At 210 minutes, maternal blood and feto-placental tissues were removed for radioactivity measurement. Folate status and ethanol treatment had no effect on the distribution of 3H-folate in maternal circulation. However, contrary to the hypothesis, the uptake of 3H-folate by feto-placental tissues was increased in folate deficiency and by ethanol treatment, indicating that folate transfer was not impaired by the ethanol treatment. Other possibilities are discussed.