Inclusion Criteria: Community dwelling, independently ambulatory adults with mild to moderate PD (Stages 2, 2.5, and 3 on the modified Hoehn and Yahr scale) will be included. For inclusion, study subjects must have a diagnosis of PD made by their attending neurologist using criteria from the UK Brain Bank (e.g., at least two of the cardinal signs of PD [i.e., bradykinesia, resting tremor, rigidity, postural instability]); without PD medication other known or suspected causes of parkinsonism. They must be on a stable regimen for at least one month prior to enrollment, and must be receiving optimal medication management in the judgment of the examining neurologist.