A 22-month-old castrated male ferret developed acute pelvic limb paresis. Radiographs and computed tomography revealed a soft tissue mass with associated bony lysis of 15, and ultrasound-guided fine needle aspirates suggested that it was a lymphoma. Treatment with prednisone at immunosuppressive doses did not produce any detectable improvement in the ferret's clinical signs and it became moribund less than two weeks after they developed. A postmortem biopsy confirmed the presence of a lymphoma which had invaded the vertebral bone. No viruses were detected by cell culture, or electron microscopy.