Weanling male and female mice (F0) were fed daily diets containing 4-deoxynivalenol (DON) at concentrations that resulted in a dose of 0 or 2.0 mg/kg body wt in Experiment I and 0, 0.375, 0.75, or 1.5 mg/kg body wt in Experiment II. The test diets were continuously fed to the F0 parents and their progeny for the entire duration of these two experiments, which were similar in design. After 30 days of dietary feeding, the mice were allowed to mate within experimental groups for a maximum of three 5-day trials. Females found to have mated successfully were allowed to litter normally. The F1a progeny from 10 dams of each control and 1.5-mg DON/kg groups were cross-fostered at birth, whereas all of the remaining F1a progeny were reared by their natural dams. The progeny were examined until 21 days of age and discarded. The F0 mice were rebred. The females bred to produce the F1b litters were killed on Day 19 of gestation and their fetuses were examined for gross, visceral, and skeletal malformations. Reductions were observed in feed and water intakes and body weight of F0 male and female mice, the number of live pups and postnatal survivors, postnatal body weight of F1a progeny, number of live fetuses, and mean fetal weight of F1b fetuses. No adverse effects on fertility of F0 male and female mice and no major malformations in F1b were found. Cross-fostering offspring between control dams and 1.5-mg DON/kg-treated dams revealed that both postnatal survival and body weight were adversely affected by prenatal exposure as well as by a combined pre- and postnatal exposure. Male and female Sprague-Dawley rats were fed diets containing DON so as to deliver daily doses of 0.25, 0.5, or 1.0 mg/kg body wt. After 6 weeks of feeding, the rats were bred within groups and the males were then discarded. The mated females, maintained on their respective diets for the entire period of pregnancy, were killed on the last day of pregnancy and fetuses evaluated for effects on prenatal development. Except for dilation of renal pelvis and urinary bladder, the significance of which remains undetermined, no other adverse effect was observed.