Isoxaben (82558-50-7) was evaluated for three-generation reproductive toxicity. Twenty-five Wistar rats/sex/group for each parent generation were administered 0, 40, 200, or 1000 mg/kg/day of the test material in the diet. No physical signs of treatment- related toxicity were observed. Food consumption was depressed in F1 females at 1000 mg/kg/day. Significant depressions in body weight gain and body weight were4observed in F1 parental females at 1000 mg/kg/day. Absolute and relative mean liver weights were significantly increased in F0 parental male rats at 1000 mg/kg/day. No treatment-related effects on mating performance or fertility were observed. No treatment-related differences in mean gestation length, mean gestation survival, or live litter size were observed during the first F1 delivery trial. During the second F1 delivery trial, mean live litter size was significantly depressed at 1000 mg/kg/day. Mean body weights of the progeny of dams were significantly depressed at 1000 mg/kg/day. Sex distribution was unaffected by treatment. Increased incidences of exencephaly and microphthalmia were observed at 1000 mg/kg/day. The no-effect level for reproductive toxicity was 200 mg/kg/day.