The influence of lactate on the potential developmental toxicity of high doses of aluminum (57.5 mg/kg/day) was evaluated. Three groups of pregnant Swiss mice were given by gavage daily doses of Al(OH)3 (166 mg/kg), aluminum lactate (627 mg/kg), or Al(OH)3 (166 mg/kg) concurrent with lactic acid (570 mg/kg) on gestational days 6-15. An additional group of pregnant mice received lactic acid (570 mg/kg) during the same period. Cesarean sections were performed on gestation day 18, and live fetuses were sexed, weighed and examined for morphological defects. Maternal toxicity was observed in the groups treated with aluminum lactate, and Al(OH)3 concurrent with lactic acid. The reproductive data did not show embryotoxic effects in any group, whereas fetal body weight was significantly reduced in the aluminum lactate group. In this group, morphological changes included cleft palate and an increased incidence of parietals with delayed ossification. Although not statistically significant, the incidence of skeletal variations was also increased in the group given Al(OH)3 concurrent with lactic acid. Taken together the present data, as well as the results of previous studies strongly suggest that the consumption of high doses of aluminum-containing compounds should be avoided during pregnancy.