Hyperadrenocorticism is a frequently occurring disease in middle-aged ferrets. It is caused by a neoplasm of theadrenal cortex. Otherwise than in dogs and cats, hyperadrenocorticism in the ferret is always independent ofadrenocorticotropic hormone (ACTH). The tumor of the adrenal cortex can be removed surgically, mostly withsatisfying results. After surgery, a regression of symptoms occurs after two to eight weeks, and the animals arewithout symptoms after five to eight months. In recent years, there has been a growing interest in using a chemicaltherapy aimed at decreasing hormone production through the administration of GnRH agonists. These agonistsinitially cause a temporary increase of the sex steroids, and then a long-term decrease of them through desensitizationof the GnRH receptors. A deslorelin implant seems to be a promising alternative for the surgical treatment ofhyperadrenocorticism in ferrets. Some authors even recommend it as a standard preventive treatment after neuteringin both genders and for every ferret over four years of age. Moreover, it is an excellent alternative for surgicalcastration.