The clinical details of 100 cases of histologically confirmed Parkinson's disease were examined and correlated with pathologic findings. Age at disease onset (mean, 62.4 years), disease duration (mean, 13.1 years), and age at death (mean, 75.5 years) were similar to those in previous smaller series. Asymmetric, tremulous onset was most common, although 23% of patients had no rest tremor. Motor fluctuations and dyskinesias occurred in 60% of levodopa-treated patients. All patients had clinical parkinsonism; however, 12 had atypical clinical features of Parkinson's disease, including severe early dementia, fluctuating confusional states, no response to levodopa, and early marked autonomic disturbance. Neuropathologic examination found coexistent Alzheimer-type change in 17 cases and striatal abnormality--mainly vascular--in 34 cases. Cortical Lewy bodies were present in all cases, but only four satisfied proposed criteria for diffuse Lewy body disease. Dementia occurred in 44% of cases; 29% had Alzheimer's disease, 10% had numerous cortical Lewy bodies, and 6% had a possible vascular cause; in 55% no definite pathologic cause was found. Nigral cell loss correlated with disease duration and severity. Although the general pattern of disease conformed to traditional descriptions, the findings broaden the present clinical and pathologic spectrum of Parkinson's disease.