Thirty patients with heperthyroidism were investigated for triiodothyronine (T3), thyroxine (T4), thyroid stimulating hormone (TSH), thyromicrosome antibody (TMA), thyroglobulin antibody (TGA) and hydrocortisone before and after operation. The levels of serum T3, T4, TGA, TMA were markedly decreased after operation, and the level of hydrocortisone farther decreased from the preoperative low level. But only a little decrease in TSH level was found as compared with that before operation. The assay of these hormones and antibodies has very important clinical significance for judgement of the effect of operation and prevention of crisis of hyperthyroidism.