Pregnant Sprague-Dawley rats were exposed to 0, 40, or 80 ppm of acrylonitrile by inhalation for 6 hrs per day from days 6 through 15 of gestation. Inhalation of 80 ppm, a maternally and embryonally toxic concentration, did not significantly alter the incidence of any single malformation. The incidence of total malformations, when considered col- lectively, was marginally increased (p=0.06) at 80 ppm. Also noted at 80 ppm was a low incidence of the same mal- formations seen in an earlier study in which pregnant rats were given acrylonitrile by gavage. At 40 ppm, significant maternal toxicity was evident, but no signs of embryotoxicity, fetotoxicity, or teratogenicity were seen. In conclusion, findings suggestive of a teratogenic effect were seen in the offspring of pregnant rats inhaling 80 ppm but not 40 ppm of acrylonitrile.