A placebo-controlled double-blind dose-ranging randomized trial of inosine will be conducted in early PD. Ninety untreated subjects diagnosed with idiopathic PD and with a serum urate below the population mean (~6 mg/dL) will be enrolled at 17 North American sites and randomized to one of three treatment groups (n=30): 1) placebo, 2) inosine dosed to produce a mild elevation in serum urate, and 3) inosine dosed to produce a moderate elevation. Tolerability, validity (urate elevation), dosage and symptomatic efficacy will be assessed after 12 weeks of treatment. Contingent on adequate tolerability and validity as assessed in this short-term analysis, the study will continue for 2 years total duration with 2 groups (placebo and a merged single inosine dosing group) or the original 3 to assess long-term tolerability and safety, which will focus on main known risks of urolithiasis and gouty arthritis and the theoretical risk of cardiovascular disease.