The sacral segments of the spinal cord in 15 cases of amyotrophic lateral sclerosis and 7 control cases were investigated using peptides immunocytochemistry. A rich supply of somatostatin-, enkephalin- and substance P-immunoreactive fibers and terminals were found in common with the intermediolateral cell column in Onuf's nucleus, but not with the motor neurons in ventral horn. Furthermore, there was no significant difference with peptides innervation between ALS and control cases. Onuf's nucleus, though located in the ventral horn of the upper sacral segment, has a rich supply of peptidergic innervation which suggests that this nucleus does not represent merely somatic motor neurons, but also represents autonomic neurons. This may be related to sparing of Onuf's nucleus along with the autonomic sacral intermediolateral nucleus in ALS.