To compare the safety and efficacy of low dosages of pramipexole given twice daily (bid) in early Parkinson's disease (PD) with those of a standard 3 times daily (tid) regimen in a randomized, double-blind, placebo controlled trial involving 311 early PD patients not receiving dopaminergic treatment. Subjects were randomly assigned and followed on assigned treatment for 12 weeks with pramipexole at dosages of 0.5 mg bid, 0.75 mg bid, or 0.5 mg tid, or matching placebo. All subjects were dosed 3 times daily, with placebo if necessary, to maintain blinding. The primary outcome was the change from baseline to Week 12 in the Unified Parkinson Disease Rating Scale (UPDRS) total score (Parts I-III). All active dosages had similar antiparkinson efficacy showing reductions of 4-5 UPDRS points relative to placebo (p < 0.0001) for each comparison. Somnolence, fatigue, nausea, constipation, and peripheral edema were more common in the active treatment groups than in the placebo group, but their frequency did not vary by dosage. In this fixed dosage, randomized study pramipexole administered twice daily at a total daily dosage of 1.0-1.5 mg daily was of comparable efficacy and tolerability to a dosage of 0.5 mg tid over a 12-week treatment period in early PD.