Objective To investigate the diagnosis and treatment. Of primary hyperthyroidism and concurrent thyroid microcarcinoma. Methods A retrospective analysis of 32 cases of primary hyperthyroidism and concurrent thyroid microcacinoma proved by postoperative pathology and were admilted between January 1994 and December 2002.Resulth The morbidity was 1.07%.No case had been diagnosed before operation.All of 32 cases underwent bilateral subtotal thyroidectomy.All cases showed diffase goiter and 11 cases showed small thyroid nodules at operation. There was no evidence of lymph node metastasis. No case had reoperation. No case of recurrent hyperthyroidism nor cancer was found during the 1 to 10 (mean5.5)years follow up. Conclusion The clinical diagnosis of primary hyperthyroidism and concurrent thyroid microcarcinoma is difficult and chiefly depends on postoperative pathology. Surgical treatment gives good results and has a better prognosis ,but long term follow up is still needed.