Adult Sprague-Dawley rats were fed diets containing 0, 0.25, 0.5, 1.0, or 2.0% of the food additive brominated vegetable (soybean) oil (BVO) for 2 weeks prior to mating. After conception, the diets were continued throughout gestation and lactation for the females. The same diets were also provided to the dams' offspring throughout their development (up to 90–120 days of age). BVO at 2.0% of the diet completely blocked reproduction. BVO at 1.0% of the diet severely impaired conception, reduced maternal body weight, and produced slightly reduced litter sizes but no evidence of malformations. At this dose postnatal mortality was high, and survivors showed impaired growth and severe behavioral impairments on a battery of standardized tests of functional development. After weaning, adequate data could not be obtained because of the high mortality rate in this group. BVO at 0.5% of the diet produced less reproductive interference and much less offspring mortality or impairment of growth, but produced behavioral impairments almost as severe as seen in the BVO 1.0% group. In addition, this group exhibited severely reduced postweaning activity, delayed vaginal patency development, and reduced day-90 weight. BVO at 0.25% of the diet produced reproductive deficits similar to the BVO 0.5% group, but less severe effects on growth and behavioral development. This group showed no significant increase in offspring mortality. The data demonstrate clear evidence of dose-related physical and behavioral developmental toxicity.