To test whether Parcopa, a new Orally Disintegrating Tablet of Carbidopa-Levodopa, has a faster onset of action, changes in the UPDRS Motor Exam score at intervals after a single dose of Parcopa or Sinemet are being compared in 10 subjects with Parkinson's disease. Subjects 40 years or older having idiopathic PD with Hoehn and Yahr state II or III are eligible if taking a stable dose of < 200 mg carbidopa and < 2000 mg levodopa daily. At both treatment visits, either Parcopa or Sinemet, plus a placebo of the opposite tablet (ODT or conventional) are administered. The dose is the same as the subject's prestudy regimen. The primary efficacy variable, time to onset of action, is the first postdose time when a 30% decrease (30% improvement) in the total score is achieved. All UPDRS evaluations are done by a rater blinded to the active treatment received by the subject.