Sleep disorders are common in Parkinson's disease (PD) and a significant cause of impairment of function in already disabled individuals. Almost all patients with PD report disturbed sleep, including excessive daytime sleepiness (EDS), disorders of initiating and maintaining sleep (DIMS) or parasomnias.1 The underlying pathology associated with PD and medication effects have both been implicated in the sleep disorders affecting these patients. EDS has become the focus of attention because of its effect on quality of life and impairment in driving and predisposition to traffic accidents. Its prevalence has been estimated between 15-50%. Treatment of EDS has become an important factor in the management of the PD patient, and the recent introduction of modafinil, a wakefulness promoting agent approved for narcolepsy, has led to increasing off-label use of this agent. Prior to modafinil, amphetamine and methylphenidate, two classical psychostimulants, were the agents of choice in treating EDS. However, these agents also have a direct effect on the dopaminergic system. They increase both sleep and REM latency, while reducing total sleep time and REM sleep. By comparison, the mechanism of action of modafinil is unknown, yet distinct from that of the psychostimulants. A direct comparison of the effect on EDS of modafinil with classical psychostimulants is lacking. The overall goals of this research proposal are to determine which agent is most effective in treating EDS in PD patients by using an open-label randomized control study comparing efficacy, onset of action and tolerability.