One hundred and fifty-seven patients with Graves' disease treated with 131I from July 2001 to March 2003 were studied retrospectively. According to the thyroid function one year after 131I therapy, the patients were divided into 3 groups: remission group with normal FT3, FT4, partial remission group with above normal levels of FT3, FT4, and hypothyroid group with lowered levels of FT3, FT4. Prior to 131I treatment the thyroid-stimulating hormone receptor antibody (TRAb) was positive in 88.5% of the patients. After the therapy, TRAb levels rose transiently and reached the peak within 3-6 months and then dropped gradually thereafter. The weight of pretreatment thyroid, high levels of TRAb (≥405 U/L) and FT3, FT4 were predictors for the outcome of treatment.