Abstract: Two-hundred-eighty-four patients’ with Graves disease were followed up retrospectively or prospectively for from 6 months to 25 years after cessation of antithyroid drugs.The remission rate was found to be 65.6%（149/227）at 2 years,53.5%（68/127）at 5 years and 38.8%（19/49） at 10 years and over.In order to study the remission rate in relation to the duration of treatment,the patients were divided,according to the time of therapy,into 3 groups:short-term（6.7±1.5mos）,mid-term（14.3±2.3mos）and long-term（26.3±8.3mos）.The remission rate was found to be the lowest in the short-term group,higher in the mid-term group,and the highest in the long-term group,although the diffference was statistically insignificant.T₃ suppression test and TRH stimulation test were performed upon cessation of treatment in 62 cases and repeated in 20 cases 1 year later.Significant difference in the response to T₃ suppression test between different groups was noticed immediately following cessation of therapy,but no similar difference was demonstrated 1 year later.The present study indicates that serum T₃ and T₄.the size of thyroid before treatment and T₃ suppression test have certain value in predictine the result of antithyroid drug therapy and that,since most of the patients obtaining long-term remission are those having received short-term therapy,a 6-month drug administration seems to be just as effective as therapy of longer durations.