Neuronal vacuolation, involving the cerebellar roof nuclei, Purkinje cells, selected nuclei of the brain stem, thalamus, Clarke's column, anterior and posterior horns of the spinal cord, visceral autonomic ganglia and myenteric plexus, as well as axonal degeneration of the white matter of the brain stem, cerebellar pedunculi, dorsolateral columns of the spinal cord and ventral roots of the spinal cord, were observed in two young Rottweiler dogs which were clinically afflicted with hind limb weakness progressing to paraparesia, ataxia, intention tremor, and difficulty in swallowing and barking. The absence of modifications in Bcl-2 and Bax immunoreactivity, a lack of strong c-Jun/AP-1 (N) immunoreactivity in vacuolated cells, and the absence of DNA breaks, as seen with the method of in situ end-labeling of nuclear DNA fragmentation, all suggest that there is no involvement of the apoptotic pathway in vacuolated cells in this new neurodegenerative disorder.