Objective To investigate the effect of operation for hyperthyroidism assoiciated with hypokalemic periodic paralysis(HPP).Methods We retrospectively analysed the clinical data of 121 cases of hyperthyoidism associated with HPP.Among them 81 patients received subtotal thyroidectomy after taking Lugol solution for 2 weeks;40 patients received non-operative therapy.Results The plasma potassium,T3,T4,TSH and BMR levels of patients who received subtotal thyroidectomy were all normal 1 week post-operatively,Only 2 patients suffered symptoms of relapse at follow up of 0.5-10 years,with cure rate of 97.5%;8 of the patients who received non-operative therapy recovered,with cure rate of 20.0%.Conclusions Operation for hyperthyroidism associated with HPP could cure HPP and hyperthyroidism simultaneously.The therapeutic efficacy of operation is rapid and stable,and is markedly better than that of non-operative therapy.