The effect of levodopa on the mortality of patients with Parkinson's disease was investigated in 349 patients treated with levodopa or levodopa combined with decarboxylase inhibitor during 1969-1975 inclusive. During the study period, 61 patients died. The expected mortality was 32.99 resulting in a ratio of actual to expected deaths of 1.85. The excess mortality was accounted for by patients with a severe disease at entry and especially, by the less favorable effect of levodopa treatment than in the living patients. In comparison with the prelevodopa era, the reduction of mortality and the increase of life expectancy of patients with Parkinson's disease during levodopa treatment possibly reflect the decrease of the early mortality due to Parkinson's disease.