Anxiety disorders, particularly generalized anxiety, panic, and social phobia, occur in up to 40% of patients with Parkinson's disease (PD). This rate is higher than in normal or other disease comparison populations. Current evidence suggests that anxiety may not be a psychological reaction to the illness but rather may be linked to specific neurobiologic processes accompanying PD. Anxiety in PD often coexists with depression. The optimal pharmacologic treatment for anxiety in patients with PD has not been established, but available information about the use of anxiolytics in PD is reviewed. Further study of the relationship between anxiety and PD may provide an excellent opportunity to clarify the neurobiologic substrate of anxiety itself.