The primary purpose of this study is to determine whether sumanirole, at three different dose levels, is effective and safe in the treatment of the signs and symptoms of early Parkinson's disease

Inclusion Criteria:

Idiopathic Parkinson's disease < 7 years duration

Modified Hoehn and Yahr Scale Stages I through III

Age greater than or equal to 30 years old

Patients or their partners must use adequate contraceptive methods

Patients who are willing and able to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures and do not plan on traveling extensively during the study

Exclusion Criteria:

Atypical Parkinson's disease syndromes due to drugs, metabolic disorders, encephalitis, or degenerative diseases.

Levodopa received for 1-year accumulated interval in the last two years.

Dopamine agonist medications or catechol-o-methyl transferase inhibitors in the 30 days prior to baseline.

Unstable dose regimes of hypnotics, anxiolytics or antidepressants

Dementia

History of stereotaxic brain surgery, psychosis or active epilepsy within past year.

Participation in clinical trial within the previous 30 days.

Malignant melanoma or history of melanoma

Significant medical or pshychiatric condition