The past few years have seen important advances in our understanding of the causes of Parkinson’s disease (PD) and in our ability to optimize the symptomatic management of the motor features that characterize this disorder. This supplement reviews progress in several important areas of PD and encompasses some of the basic science that underlies current and future treatment strategies for PD. Although PD remains the focus of attention of much of the movement disorder community, interest has recently been developing in restless leg syndrome (RLS), which may be the most common movement disorder of all. Again, advances have been made both in the understanding and the treatment of this disorder, and these are reviewed in this supplement. The discovery that MPTP was capable of producing parkinsonism in humans, in other primates, and in rodents provided the opportunity to generate animal models of PD that would be useful both in identifying biochemical mechanisms that may underlie selective dopaminergic degeneration and in the study of pharmacologic agents that may improve symptomatic control of PD. The MPTP primate model of parkinsonism is not a perfect model for the human form of the disease. Nevertheless, it has provided several important insights into the mechanism of action of drugs and, in particular, into their potential toxicity. In this supplement, Jenner reviews the contribution that study of the MPTP model has made to the understanding of the cause and treatment of the motor complications that result from l-dopa use in PD. l-dopa remains the gold standard for the symptomatic management of the dopaminergic-related motor features of PD. Concerns that this drug may have toxicity in vitro have not been supported by any robust data that it is toxic to PD patients. Nevertheless, motor complications, in the form of “wearing-off” and dyskinesias, develop in a …