The teratogenic effects of lead acetate (Trial 1) and the possible teratogenic effect of this compound administered in combination with a fungicide containing 80% mancozeb (Trial 2) were studied in rats. The test substances were administered by gavage on Days 6-15 of gestation. In Trial 1, five groups were treated with lead acetate administered at doses of 0.1, 0.5, 1.0, 10.0 and 1000.0 mg/kg body weight (bwkg), respectively. In Trial 2, lead acetate was applied at doses of 0.1, 10.0 and 1000.0 mg/bwkg, respectively. In the latter case the dose of the pesticide was 750 mg/bwkg in all treated groups. Lead acetate was not teratogenic after a single administration. Combined administration of lead acetate and mancozeb gave rise to the following toxic effects: average maternal weight decreased during pregnancy, the ratio of live fetuses decreased after the two lowest doses, and fetal mortality increased in the lowest and in the highest dose groups. The ratio of fetal resorption was higher in all the treated groups than in the control group. A significant decrease occurred in average fetal and placental weight in each treated group as compared to the control. Maternal toxicity was expressed in paralysis of the hindlimbs in the two lowest dose groups. Maternal mortality was between 16.7 and 23.3% at the three dose levels. Phocomelia and hernia cerebri occurred as characteristic fetal developmental anomalies in all the treated groups. It is concluded that the joint administration of lead acetate and a mancozeb-containing fungicide can cause maternal toxicity, embryotoxicity and characteristic teratogenic effects.