Dyskinesia manifests overwhelmingly when plasma levodopa levels are high enough to cause anti-parkinsonian benefits, and lessens or stops when levodopa levels drop below a threshold. Thus, the subject's dyskinesia measurements must occur during a levodopa administration period. Dyskinesia measurement will occur during a two-hour levodopa cycle administered to subjects at weeks 0, 6, 24, 52, 76. It is expected that a good proportion of subjects will manifest dyskinesia within the two-year observation period, as previous studies using the most objective means to measure dyskinesia report incidence rates of 67% or greater within the first year of levodopa use. An instrument to measure dyskinesia developed by this center will be used as an additional outcome, and is expected to measure dyskinesia more accurately and with greater sensitivity than the gold standard methods of clinical rating scales.