The clinical and pathological findings in a 58-year-old Japanese man suffering from type III Machado-Joseph disease are reported. The patient became affected at the age of 50 years and presented cerebellar ataxia, progressive external ophthalmoplegia and muscular atrophy, although extrapyramidal signs were never detected throughout the whole course of his disease. His mother, sister and son presented progressive ataxia in the third or fourth decade. The mode of inheritance is considered to be autosomal dominant. Pathological examination revealed severe involvement of the dentato-rubral, ponto-cerebellar and subthalamopallidal systems, spinocerebellar tracts and Clarke's column, cranial motor nuclei including the oculomotor systems and anterior horn cells. The involvement of the substantia nigra was relatively mild, and the nerve cells in the inferior olivary nucleus were well preserved. The distal portion of peripheral nerves was severely damaged. Although the striking feature of Machado-Joseph disease is a considerable variability in the individual clinical expression, there have not been many autopsied cases of this disease and efforts to clarify the clinico-pathological correlation in each phenotype have scarcely been made. Relatively mild changes in the substantia nigra and severe involvement of the peripheral nervous system, as in our case, may be the pathological hallmarks of the type III disorder.