Objective：To improve the diagnosis for atypical parathyroid adenoma（APA） by exploring the clinical and pathological manifestations of APA. Methods：Clinical data of 11 cases of APA in our hospital were retrospectively studied. The diagnosis was confirmed by operation and pathology. Eighty-one patients with parathyroid adenomas were admitted between January 1993 and March 2010，among which 11 patients（13.6%） were diagnosed as APA （7 males，4 females；aged 22-68 year-old with an average of （39.4±13.1） year-old）. Results：There were 7 patients（63.6%） with bone disorders and 4 patients（36.4%） with bone and urinary disorders among 11 patients with APA.Serum level of calcium was raised in 10 patients，phosphorus was decreased in 9 patients and parathyroid hormone（PTH） was elevated in all patients.Histological findings were as follows：incomplete invasion of the capsule（8 patients/11 patients），focal infiltration into the fibrous connective tissue of the tumor（1 patient/11 patients），trabecular growth pattern （2 patients/11 patients），thick fibrous bands（3 patients/11 patients），atypia or mitotic figures（5 patients/11 patients） and no clear tu－mor capsule（1 patient/11 patients） were observed. Eight patients were followed up for 8-47 months，averaged （19.0±13.1） months；2 recurrent patients（25%） were observed and 1 patient developed parathyroid carcinoma proved by pathological diagnosis.Another 1 patient was found with recurrent hypercalcemia，high PTH level and ultrasonography revealed a nodule in the thyroid region，but the patient refused another surgery. Conclusions：Among considerable cases of parathyroid neoplasms，it is hard to judge the benign and malignant tumor at the initial diagnosis. Clinical manifestations of this group are in accordance with the characteristics of hyper－parathyroidism. Because of the risk of recurrence and malignancy of APA，vigilant follow-up by serum biochemistry and imaging ex－amination is recommended.