A retrospective study of 17 dogs with hyperadrenocorticism (HAC) was performed to evaluate the clinical and clinicopathological outcomes in dogs with pituitary-dependent HAC or adrenal gland-dependent HAC. Sixteen dogs were monitored at day 10, 30 and 90 then every 3 month after first presentation. In each examination, physical examination and ACTH stimulation test and client questionnaire were performed. In 17 cases, eight dogs were successfully treated with mitotane therapy (median dose 16.7 mg/kg; range 5.3 to 50 mg/kg, SID); another one dog showed favorable response, but the clients declined to further treatment before the full control of the disease had been achieved; four dogs showed poor response to treatment. One dog was euthanized due to septicemia. These results showed canine HAC can be medically managed successfully without side effects at the doses used in this study.