Intravenous injection of three doses of 50 mg Fe/kg (total dose 150 mg Fe/kg) as iron dextran into rabbits late in pregnancy (days 26, 28, and 30 of gestation) reduced the weight gain of the dams and increased fetal mortality. Three doses of 20 mg Fe/kg also increased fetal mortality, while three doses of 5 mg Fe/kg were without effect. Liver and kidney iron concentrations of the dams and offspring were markedly increased at the time of parturition by treatment with a total dose of 150 mg Fe/kg. At 6 weeks after birth the liver and kidney iron concentrations of offspring from treated dams were comparable to those from control dams. The liver and kidney iron concentrations of the treated dams were significantly reduced from the levels found immediately post-partum. In the rat, four i.v. doses of 200 mg Fe/kg as iron dextran on days 17, 18, 19, and 20 of gestation (total dose 800 mg Fe/kg) produced tremors, reduced body weight gain, and reduced food consumption in the dams. The growth and survival of the offspring were adversely influenced by these effects on the dam. The liver iron concentration in offspring of rats treated with 800 and 400 mg Fe/kg was increased at parturition, but had returned to normal at 4 weeks of age. No iron-induced pathology was evident in the offspring of either rabbits or rats after 14 and 18 weeks, respectively.