Pregnant Charles River CD(trademark)-1 mice and pregnant Charles River COBS(trademark) CD(trademark) rats, randomly assigned to one control group and two t-dodecyl mercaptan treated groups of fifty animals (25 mice and 25 rats) each, were used to determine the teratogenic potential of t-dodecyl mercaptan. Mean actual exposure levels of 22.7 and 88.6 ppm, which correspond to mean nominal exposure levels of 34 and 109 ppm and were designated groups 3 and 4, respectively, were administered by whole body inhalation exposure on gestation days 6 through 16 (mice) or 19 (rats) on a 6-hour daily exposure schedule. The control group was exposed to filtered air only on a comparable regimen. Cesarean sections were performed on all surviving mice on gestation day 17 and on all surviving rats on gestation day 20 and fetuses removed for teratologic evaluation.