We studied the neurological comorbidity of parkinsonism in 368 consecutive patients from the Lausanne Movement Disorders Registry. Only 6 patients had no neurological comorbidity. We found that 23p.100 of our patients had ischemic strokes, especially large vessel strokes, i.e three times more than in an age-matched control study performed in a recent survey in our country, which is a new finding in contradiction with previous reports mentioning that Parkinson's disease may be a protective factor against stroke. This finding opens new directions for further studies concerning some shared mechanisms in both diseases associated with age. Predominantly tremulous parkinsonism (46p.100) and progressive supranuclear palsy patients (PSP) (40p.100) had the highest prevalence of cerebrovascular disease of all subgroups of parkinsonism, especially lacunar infarcts, which is in accord with a higher frequency of hypertension in these subgroups according to a recent study of ours. Transient ischemic attacks or hemorrhages were not more frequent than in the general population. We did not find a higher frequency of head trauma except for Parkinson's disease, but a trend for a higher frequency of headache and migraine. Brain tumors were more frequent in Parkinson's disease and hydrocephalus and radiculopathies in parkinsonism in general when compared to age-matched populations from the literature. Polyneuropathies were more frequently observed in familial parkinsonism only, but myopathies and cranial neuropathies were not more frequent in our patients. Epilepsy was significantly less frequent in parkinsonism, especially in Parkinson's disease, infectious diseases of the nervous system were rarely encountered, and restless legs syndrome was surprisingly not more frequent than in a normal population. Dementia was associated in 20p.100, but multiple sclerosis is noticeably absent.