Many patients with Parkinson's Disease (PD) experience significant cognitive and mood impairment -even early in the course of the disease. These mental impairments are only partially responsive to levodopa treatment and are often as disabling as the motor impairment, particularly in mid and late stages of the disease. Investigators have recently begun a search for new agents that can effectively treat mental dysfunction of PD. Although there have been only a handful of properly controlled clinical trials of interventions targeted at amelioration of mental dysfunction in PD, progress has been made. Based on the available evidence, targeting catecholaminergic and cholinergic function may be an effective strategy for amelioration of cognitve, mood and psychiatric disturbances in PD.