Pregnant outbred albino mice (CD-1) received n-hexane once daily be gavage at doses up to 2.20 g/kg/day on days 6-15 of gestation. Other pregnant mice received higher hexane doses (up to 9.90 g/kg/day), employing a three times a day injection schedule. At the lower, once-daily doses only one dam died and no teratogenic effects occurred. Higher hexane doses (t.i.d.) were toxic: 2 of 25 dams treated with 2.83 g/kg/day, 3 of 34 treated with 7.92 g/kg/day and 5 of 33 treated with 9.90 g/kg/day died. At the 7.92 and 9.90 g/kg/day doses, the average fetal weight was significantly (p less than 0.05) reduced, but the incidence of malformations in treated and vehicle (cotton-seed oil) control groups did not differ significantly. Thus, n-hexane was not teratogenic even at doses toxic to the dam.