Domestic ferrets (Mustela putorius furo) are becoming increasingly common in the United States. They are very popular as household pets and are also used in large numbers as research animals. With the increase in ferret numbers, there has been a corresponding increase in the number and frequency of diseases described. Neoplastic conditions are at the top of the list of problems occurring in ferrets found in the United States. An exceedingly common condition is adrenal disease as a result of adrenocortical hyperplasia, adenoma, or adenocarcinoma. These conditions present as the same clinical syndrome and anyone examining ferrets in a veterinary setting can expect to see many cases of adrenal disease.