The clinical and pathological features of 35 cases with multiple system atrophy collected in the United Kingdom Parkinson's Disease Society Brain Bank (UKPDSBB) between 1985 and 1992 have been analysed. The median age of onset was 55 (range 33.3-75.8) years and median survival was 7.3 (range 2.1-11.5) years. Parkinsonism, usually asymmetric, occurred in all, and autonomic failure in all but one case. Cerebellar signs were noted in 34% and pyramidal features in 54% of the cases. Glial cytoplasmic inclusions were found in all cases with adequate fixation. Lewy bodies were detected in three cases. The substantia nigra was (usually severely) depleted of cells in all cases. With two exceptions the putamen was atrophic; the caudate and pallidum were less commonly and less severely affected. Overall nigrostriatal cell loss correlated with severity of disease at the time of death. The latest, but not the best, recorded levodopa response tended to be inversely related to the degree of putaminal degeneration. The olivopontocerebellar system was involved in 88% of the cases, the cerebellar vermis usually being more severely affected than the hemispheres. The presence of associated cerebellar pathology was, however, unrelated to the presence of cerebellar signs in life.