Rationale:Adrenocortical oncocytoma is an extremely rare tumor of the adrenal gland. Its diagnostic criteria and biological behavior has not yet reached a consensus. The purpose of this study is to investigate the clinical characteristics of adrenocortical oncocytoma.Patient concerns:The clinical data from 11 cases of adrenocortical oncocytoma were retrospectively analyzed. Five patients found the tumor incidentally during the healthy examination, and 3 cases found the tumor during the diagnostic work-up for the evaluation of flank pain or hypertension. A female patient manifested virilization, and Cushing's syndrome showed in two patients. The tumor diameter was ranging from 2.0-13.0 cm.Diagnoses:The serum cortisol, plasma aldosterone and catecholamine metabolites were used to evaluate the function of the tumors, and enhanced CT scan was used to confirm the tumor boundary, enhancement, and lymph nodes condition.Interventions:Seven cases underwent laparoscopic adrenal tumor resection, 4 patients underwent open surgery. Pathological report indicated adrenocortical oncocytoma in all cases, three of which were potentially malignant.Outcomes:The patients were followed up for 19-72 months, no local recurrence and distant metastases were detected in 3 cases of malignant potential cases.Lessons:The majority of adrenocortical oncocytoma with or without function are benign, and close follow-up observation is essential.