Rasagiline (N-propargyl-1 (R)-aminoindan) is a selective, potent irreversible inhibitor of MAO-B that possesses neuroprotective and anti-apoptotic properties in a variety of in vitro and in vivo animal models relevant to Parkinson's disease (PD). Several randomized controlled clinical trials have demonstrated the safety and efficacy of rasagiline as monotherapy in PD and as adjunctive therapy for patients receiving levodopa. In addition, the 1-year randomized, delayed-start analysis of the TEMPO study suggests that rasagiline may slow the rate of progression of PD. The randomized delayed-start paradigm has potential to differentiate short-term symptomatic effects from long-term effects of anti-parkinsonian agents. In the future, long-term trials to examine the potential disease-modifying effects of rasagiline, which incorporate biological markers as well as clinical endpoints, may further elucidate the role of rasagiline in the treatment of both early and advanced PD.