In a pilot teratology study to establish dosage levels, pregnant Charles River CD rats (5/group) were orally exposed to acetonitrile by gavage at dosage levels of 0, 200, 375, 750, 1500 and 3000 mg/kg/day on gestation days (GD) 6-19 at a constant volume in distilled water vehicle. Toxicity was evidenced by severe loss in maternal body weight and dry red matter on the face and yellow-brown stained anogenital haircoats prior to death in all but the lowest-dose and control groups. An increase in the mean number of early resorptions was observed in the 375 mg/kg group. Marked mortality included 3 rats dying by GD 20 in the 375 mg/kg group. All rats died in the higher dose levels. By GD 18 in the 750 mg/kg/day group, by GD 18 in the 1500 mg/kg/day groups, and by GD 10 in the 3000 mg/kg/day group.