Placental transfer of glucose and alanine analogs was studied at term in ethanol-fed and control rats. Ethanol was provided as 30% of the caloric intake throughout gestation. Control groups received isocaloric liquid diet without ethanol by pair-feeding (PF) or ad libitum (AF). On the 22nd day of pregnancy, the rats were injected with a mixture of [3H]2-deoxyglucose and [14C]alpha-aminoisobutyric acid. The ratios of fetal:maternal plasma radioactivities 1 hr later were used to compare placental transfer between the groups. Mean +/- SE body weight of EF fetuses (4.54 +/- 0.07 g) was significantly lower than that of PF (4.88 +/- 0.06 g) or AF (5.17 +/- 0.09 g) fetuses. Maternal ethanol ingestion reduced placental transfer of 2-deoxyglucose and alpha-aminoisobutyric acid by 12% and 35%, respectively. Placental transfer of both analogs was not affected in the PF controls. The weight of EF fetuses correlated (p less than 0.001) with transfer of 2-deoxyglucose to the fetus. This relationship was also found in the control groups. Fetal body weight did not show a strong correlation with alpha-aminoisobutyric acid transfer. Thus, impaired transfer of glucose to the fetus may play a significant role in the growth retardation observed in fetuses of ethanol-fed rats.