Acrylonitrile (CAS No. 107-13-1) was evaluated for developmental toxicity. The test material was administered in pregnant Sprague-Dawley rats (30/group) exposed to 0, 40, or 80 ppm by inhalation for 6 hours per day from days 6-15 of gestation. No signs of altered gross appearance or behavior were observed among dams. The mean body weight of pregnant rats at 40 ppm or above was significantly decreased on days 10, 16, and 21 of gestation. The body weight gain of the dams was significantly decreased at 40 ppm or above during days 6-9 and 10-15 of gestation but not on days 16-20 of gestation. The food consumption of the dams at 40 ppm or above was significantly decreased on days 6-8 of gestation and significantly increased on days 15-17 and 18-20 of gestation. The water consumed by the pregnant rats at 40 ppm or above was increased on days 9-20 of gestation. The incidence of pregnancy was not affected at any of the doses. At both treatment doses, the mean litter size, incidence of resorptions, and the average fetal body measurements were not significantly altered. Total major malformations (short tail, missing vertebrae, short trunk, missing ribs, omphalocele, and hemivertebrae) when considered collectively were slightly increased at 80 ppm (p=0.06) comparedto controls. It was concluded that maternal toxicity was observed at 40 ppm and malformations suggestive of a teratogenic effect at 80 ppm.