Several lines of evidence indicate that people with Parkinson's disease are impaired at detecting their own motor errors. In the present study, we use a component of the event-related brain potential called the error-related negativity (ERN) to ask whether a high-level, generic error-processing system is compromised in Parkinson's disease. We recorded the electroencephalogram (EEG) from nine patients with mild to moderate Parkinson's disease and from nine normal control subjects while they performed a choice reaction time task. We found that the amplitude of the ERN was the same for both populations, indicating that the error-processing system associated with the ERN is not severely compromised in this Parkinson's disease population. These results are discussed in terms of disease progression.