The prevalence of pale bodies and Lewy bodies was studied in the substantia nigra of 12 patients with typical Parkinson's disease (PD), in 5 patients with diffuse Lewy body disease (DLBD), and in a group of neurologically normal controls. Anti-ubiquitin antibodies labelled pale bodies and Lewy bodies in typical PD and DLBD, and there was a strong positive correlation between numbers of ubiquitin-immunoreactive pale bodies and Lewy bodies. BF10, a monoclonal antibody against a phosphate-dependent epitope of neurofilament 155-kDa polypeptide subunit, immunolabelled 57% of Lewy bodies and 15% of pale bodies in typical PD. Some pale bodies and Lewy bodies were seen in the substantia nigra of 2 of 5 neurologically normal, aged controls, probably representing "incidental PD". We conclude that there is a close relationship between pale bodies and typical Lewy bodies in the substantia nigra in clinical varieties of PD, and that these inclusions share antigenic determinants. If pale bodies and Lewy bodies reflect separate aspects of the cellular pathology in PD, their formation probably occurs in parallel. Alternatively, these observations may suggest that pale bodies represent a stage in the formation of Lewy bodies.