Timed-pregnant (=33 females per group) and virgin (10 females per group) Swiss (CD-1) mice were exposed to 0 (filtered air), 200, 1000, and 5000 ppm n-hexane (99.2% purity) vapor in inhalation chambers, 20 h/day, for a period of 12 consecutive days. Plug-positive females were exposed on 6-17 days of gestation (dg). Maternal body weight at sacrifice (18 dg) and total cumulative weight gain for dams in the 5000-ppm exposure group were significantly reduced with respect to controls; however, this was due to an exposure-correlated reduction in gravid uterine weight, not to a decrease in extragestational gain. An exposure-correlated decrease in the gravid uterine weight to extragestational weight gain ratio (significant for the 5000-ppm group) occurred in the absence of an effect on placental weight. Gestational exposure to n-hexane resulted in an increase in the number of resorbed fetuses for all exposure groups relative to the control group; however, the increases were not directly correlated to exposure concentration. Gestational exposure of CD-1 mice to n-hexane vapors appeared to cause a degree of concentration-related developmental toxicity in the absence of overt maternal toxicity, but the test material was not found to be teratogenic.