Background: The threat of levodopa-induced dyskinesias often influences early treatment decisions in those with Parkinson disease. Objective: To determine the long-term risks of levodopa-associated dyskinesias of any severity, dyskinesias sufficient to require medication adjustment, and dyskinesias failing medication adjustments. Design: The medical records linkage system of the Rochester Epidemiology Project was used to identify all incident Parkinson disease patients treated with levodopa (1976-1990). All records were independently reviewed by 2 neurologists who recorded demographic and drug data, dates when dyskinesias were initially identified, and dates when dyskinesias were sufficient to require medication changes; dyskinesias not controlled by drug adjustments were also tabulated. Results: We identified 126 incident Parkinson disease patients treated with levodopa for at least 2 months. By Kaplan-Meier analysis, the estimated rate of dyskinesias was 30%by 5 treatment years and 59%by 10 years. However, the rate of dyskinesias requiring medication adjustment was estimated to be only 17%by 5 years and 43%by 10 years. At 10 treatment years, the rate of dyskinesias that could not be controlled with medication adjustments was estimated at only 12%. An increased risk was associated with younger age and higher initial levodopa dose, but not with sex. Conclusions: Levodopa-associated dyskinesias can be expected to develop in nearly 60%of patients in our community after 10 years, but these will be severe enough to require medication adjustments in only 43%of patients. At 10 treatment years, nearly 90%of these patients can expect to be spared dyskinesias that could not be controlled by drug adjustments. This population-based study suggests dyskinesia risk may not be a major concern for most Parkinson disease patients. Background: The threat of levodopa-induced dyskinesias often influences early treatment decisions in those with Parkinson disease. Objective: To determine the long-term risks of levodopa-associated dyskinesias of any severity, dyskinesias sufficient to require medication adjustments, and dyskinesias failing care adjustments Design: The medical records linkage system of the Rochester Epidemiology Project was used to identify all incident Parkinson disease patients treated with levodopa (1976-1990). All records were conducted by 2 neurologists who recorded demographic and drug data, dates when dyskinesias were initially identified, and dates when dyskinesias were sufficient to require school changes; dyskinesias not controlled by the drug adjustments were also tabulated. Results: We identified 126 incident Parkinson disease patients treated with levodopa for at least 2 months. By Kaplan-Meier analysis, the estimated rate of dyskinesias was 30% by 5 treatment years and 5 9% by 10 years. However, the rate of dyskinesias requisite was only 17% by 5 years and 43% by 10 years. At 10 treatment years, the rate of dyskinesias that could not be controlled with adjusted was was estimated at only 12%. An increased risk was associated with younger age and higher initial levodopa dose, but not with sex. Conclusions: Levodopa-associated dyskinesias can be expected to develop in nearly 60% of patients in our community after 10 years, but At 10 treatment years, nearly 90% of these patients can expect to be spared dyskinesias that could not be controlled by drug adjustments. This population-based study suggests dyskinesia risk may not be a major concern for most Parkinson disease patients.