Patients with Parkinson's disease who develop disabling levodopa-induced motor fluctuations have a stronger therapeutic response than those who experience a more modest but stable response. A difference in the histopathological lesion between the two groups might be responsible. Case records from 97 patients with pathologically proven Parkinson's disease were reviewed to determine the pattern of levodopa response. Pathological findings for fluctuating and non-fluctuating cases were compared. Patients with motor fluctuations had a younger age of onset and longer disease course (P < 0.001), although mean age at death was almost the same. Four milestones of advanced disease (frequent falls, visual hallucinations, cognitive disability and need for residential care) occurred at a similar time from death in each group; this interval was not proportionate to the disease duration. There were no significant differences in the severity or distribution of Lewy body or other pathologies. Irrespective of the pattern of levodopa response, patients reach a common pathological endpoint at a similar age, and the duration and manifestations of end-stage disease are alike. A non-linear or exponential time relationship may govern the late clinical and pathological progression of Parkinson's disease.