The objective of this multiple center clinical trial will be to determine safety, tolerability and efficacy of one or more agents as neuroprotective therapies for Parkinson's disease (PD). The Movement Disorders Clinic at Indiana University will make a commitment to enroll 84 subjects in three and a half years for the pilot studies (n=12) and for the main clinical trial (n=72). The duration of the study will be 6-8 years. The investigators and the nurse coordinator possess clinical expertise in treating PD and have substantial experience in executing clinical protocols for PD. Recruitment of subjects will be from PD clinics at a tertiary care center and at a country hospital to maximize the potential for encouraging minorities and women to participate in these studies. The agents under study and the final design of the trials have yet to be determined.