For many years, the fungus Fusarium moniliforme was considered a benign inhabitant of corn throughout the world. Its status changed, however, with the discovery of its toxic metabolites, the fumonisins. Fumonisin B1, in particular, has been implicated as a causative agent for several animal and human diseases. Despite toxicity studies in animals and human epidemiological studies, there is no knowledge of reproductive effects of the compound. This study is one of a series of proposed studies that would allow extrapolation to humans. Pregnant rats were gavaged with fumonisin B1 at dose levels of 0, 1.875, 3.75, 7.5, or 15 mg/kg on gestation days 3-16. On day 20, cesarean sections were performed, and reproductive and teratological parameters were measured. At 15 mg/kg, maternal feed consumption and body weight gain were significantly decreased, but fluid consumption was not affected. Maternal reproductive findings were not affected. Significant decreases in fetal body weight and crown-rump length were seen at 15 mg/kg. This study was supported by NIESH/NTP.