We sought to determine the continued benefit and the pattern of motor complications of long-term levodopa treatment in Parkinson's disease. Patients were evaluated between 1968 and 1996. Only those who had an adequate levodopa trial and in whom autopsy revealed Lewy body Parkinson's disease were included. Total levodopa and mean daily dose were calculated in each case. Dyskinesia, wearing-off and on-off were collectively classified as motor adverse effects and reported as cumulative incidence. Forty-two patients (male, 30; female, 12) with mean 15.9 years of illness and 9.1 years follow-up received on average 500-mg levodopa daily over 9.8 years. Seventeen of 21 patients assessed during the last 18 months of life reported some motor benefit. Adverse effects were seen in 71.4% of patients. The most common was dyskinesia, in 61.9%; wearing-off in 35.7%; and on-off in 16.7% of patients. The earliest adverse effect was dyskinesia and the last to emerge was on-off. Isolated dyskinesia was seen in 35.7% and wearing-off in 7.1% of patients; 15.5% of patients developed dyskinesia after 2.6 years and 31% after 6.4 years on levodopa. We concluded that levodopa benefit declined and adverse effects increased with time. Dyskinesia was the earliest and the most common isolated adverse effect. © 2002 Movement Disorder Society.