This collection of review articles provides detailed clinical descriptions and treatment recommendations for the important, but often unrecognized, nonmotor dysfunctions of Parkinson's disease. Topics range from behavioral abnormalities and autonomic dysfunction to sleep-related and sensory dysfunction, and include depression and anxiety, dementia, psychosis, obsessionality, gastric and intestinal dysfunction, impaired sexual function, insomnia, excessive daytime sleepiness, and sleep apnea. The authors review what is known about each type of dysfunction, discussing clinical features, methods of diagnosis, and treatment.