To obtain information on the possible repeated-dose oral toxicity of β-bromostyrene and its reversibility, Crl: CD (SD) rats were administered β-bromostyrene through gavage at 0, 30, 125, and 500 mg/kg/day once for 28 days, followed by a 14-day recovery period. In the 500 mg/kg group, decrease in spontaneous movement was observed in all males and females on the first dosing day, and one female rat died on Day 3. There were no significant changes in body weight or food consumption. An increase in urine volume and decrease in urine osmolality were observed in males receiving 125 mg/kg and above, and an increase in urine volume was observed in females receiving 500 mg/kg. On blood biochemical examination, increases in total cholesterol, phospholipids, triglycerides, total protein, albumin, inorganic phosphorus, and/or chlorine were observed in the 125 and/or 500 mg/kg groups. Histopathologically, eosinophilic bodies of tubular cells and/or renal tubular degeneration were observed in the kidneys of males in the 125 and 500 mg/kg groups. In the thyroid, hypertrophy of follicular cells was observed in females receiving 125 mg/kg and above and males receiving 500 mg/kg. Furthermore, centrilobular hepatocellular hypertrophy was observed in both sexes receiving 500 mg/kg. These changes observed at the end of the dosing period disappeared or were reduced after the recovery period. Based on these results, the no-observed-adverse-effect-level of β-bromostyrene was judged to be 30 mg/kg/day for both sexes.