Reduction of goiter size is one of the criteria necessary to determine clinical remission in antithyroid drug (ATD)-treated Graves' patients. To facilitate goiter reduction or to achieve quick remission, a short-term steroid treatment was administered to 5 Graves' patients. These patients had been treated with ATD for a considerable period of time, had maintained euthyroidism with negative or weak thyrotropin-binding inhibitor immunoglobulin (TBII), but still had an enlarged goiter and remained T3 unsuppressive. Betamethazone was initially given 1.5 mg daily and then gradually tapered to 0 mg for 3 months. Compared to the 6-month observation period or the pre-medication period, goiter reduction exceeding 0.7 cm was achieved in all 5 patients during the steroid treatment. These reductions partly reversed to an extent smaller than pre-treatment levels in 2 patients, but continuous goiter reductions were observed for at least 3 months after steroid cessation in 3 patients. In 2 of these reduced goiter patients, T3 suppressibility was confirmed, and they were diagnosed in remission. During steroid administration, serum T3 and TSH concentrations were lowered but reversed shortly, serum fT4 concentrations did not change, and TBII levels became negative in all patients including the 2 with weak positive values before the treatment. In conclusion, a short-term steroid treatment for goitrous ATD-treated Graves' patients appears promising in achieving goiter reduction or remission.