Research evidence suggests that voluntary exercise may be beneficial in restoring motor skills traditionally lost in Parkinson’s disease (PD). Levodopa pharmacotherapy remains the most effective treatment for PD, but is often associated with the genesis of disabling motor response complications (MRCs). This study was designed to investigate the effects of voluntary exercise on these MRCs in 6-hydroxydopamine (6-OHDA) hemiparkinsonian rats. Two weeks after rendered parkinsonian, half of these animals received twice-daily levodopa while the other half received twice-daily vehicle. An equal number of animals in each drug treatment group underwent exercise (2 hrs twice daily, 14 days) after drug injection, and the other half served as controls. Voluntary exercise therapy when combined with levodopa acted to provide a substantially greater attenuating effect on the forelimb deficits (p < 0.05) and the shortened motor response (p < 0.05) produced by chronic levodopa therapy. These results suggest that mechanisms mediated by voluntary exercise could be crucial for an accurate understanding of the pathogenesis of MRCs and further suggest novel approaches to more effective and safer therapies of PD and other dopamine disease states. McNair Scholar project. Faculty Advisor: Justin Oh-Lee.