Anatomo-clinical findings are reported in a case of central nervous system degeneration which began at age 47 and progressed over a three year period. Information obtained prior to the patient's death suggested probable spinocerebellar degeneration with amyotrophies. Postmortem anatomical examination confirmed this diagnosis but also revealed the existence of unsuspected lesions. These clinically non-manifested lesions involved severe pallido-luysian degeneration as well as numerous and diffuse senile plaques. The nosological implications of this case are discussed.