Five young Shiloh Shepherd Dogs (4 males and 1 female) related by a common sire were studied because of progressive pelvic limb weakness and incoordination. All dogs had a spastic paraparesis and pelvic limb ataxia consistent with an upper motor neuron and general proprioceptive lesion between spinal cord segments T3 and L3. Proliferative lesions involving one or more of the articular processes from the 11th thoracic vertebrae to the 2nd lumbar vertebra were observed on radiographs of the thoracolumbar vertebrae. Dorsal compression of the spinal cord was identified during imaging studies at these sites. Abnormalities of the synovial joints and bony proliferation of the involved articular processes were identified at postmortem examination in 2 dogs. The articular processes and associated vertebral arches protruded into the vertebral canal, indenting the dorsal surface of the spinalcord. Degenerative joint disease (DJD) was identified histologically. A compressive myelopathy was diagnosed in the spinal cord. These dogs were affected by a compressive myelopathy as a consequence of vertebral process DJD that likely has a geneticcomponent. The DJD could have been caused by a primary vertebral malformation or an injury to the processes at a young age causing malarticulation.