The objective of this study was to determine the effects of rasagiline as monotherapy on quality of life (QOL) in patients with early Parkinson's disease (PD). Rasagiline, a potent, second-generation, irreversible, selective monoamine oxidase B inhibitor improves PD symptoms in patients with early PD. Patients with early untreated PD were randomly assigned to once-daily rasagiline 1 mg/day, rasagiline 2 mg/ day, or placebo in a 6-month, double-blind trial (n ϭ 404). At the end of 6 months, patients entered the preplanned, activetreatment phase in which those receiving 1 mg/day and 2 mg/day of rasagiline continued on their previously assigned dosages and those receiving placebo switched to rasagiline 2 mg/day, while maintaining blinding to treatment assignments. QOL was measured with the Parkinson's Disease Quality of Life questionnaire (PDQUALIF) at 0, 14, 26, and 52 weeks after randomization. Analysis of the change in PDQUALIF scores from baseline to 6 months showed adjusted treatment effects (with 95% confidence interval) favoring rasagiline over placebo of Ϫ2.91 units (Ϫ5.19, Ϫ0.64, P ϭ 0.01) for the 1 mg/day group and Ϫ2.74 units (Ϫ5.02, Ϫ0.45, P ϭ 0.02) for the 2 mg/day. Subscore analysis attributed most of this benefit to the self-image/sexuality domain. At 12 months (n ϭ 266), with all groups receiving rasagiline for at least 6 months, no significant differences in PDQUALIF scores were seen between groups. Rasagiline improved QOL compared with placebo. This QOL improvement appears to be accounted for primarily by the symptomatic benefit of rasagiline.