Older large breed dogs, primarily of the German Shepherd type, may be presented with progressive ataxic spastic paresis. There seems to be no sex predominance. The lesion found on necropsy is diffuse degeneration of spinal cord myelin and axons in all fiber tracts, most extensive and in the mid-thoracic region, but not associated with intervertebral disc herniation, spondylosis, or osseous metaplasia of the dura. The condition is thought to be primary spinal cord degeneration of unknown cause.