Parkinson’s disease (PD) is the second most common neurodegenerative disease after Alzheimer’s disease. Traditionally, attention has focused on the motor symptomatology of PD, but it is now appreciated that the nonmotor symptoms affecting neuropsychiatric, sleep, autonomic, and sensory domains occur in up to 88% of PD patients and can be an important source of disability. Nonmotor manifestations of PD play a significant role in the impairment of disease-related quality of life. The cause of nonmotor manifestations of PD is multifactorial, but to a large extent, these manifestations are related to the nature of the neurodegenerative process and the widespread nondopaminergic neuropathological changes associated with the disease. Recognition of nonmotor disability is essential not only for ascertaining the functional status of patients but also for better appreciating the nature of the neurodegenerative process in PD. In addition, a number of nonmotor manifestations can precede the onset of motor symptoms in PD and can be used as screening tools allowing for early disease identification and for trials of possible disease-modifying interventions. This article reviews depression, sleep, and autonomic dysfunction in PD. Parkinson’s disease (PD) is the second most common neurodegenerative disease after Alzheimer’s disease. Traditionally, motor symptomatology of PD has received the most attention, but the nonmotor symptoms affecting neuropsychiatric, sleep, autonomic, and sensory domains occur in up to 88% of PD patients. 1 Nonmotor manifestations of PD play a significant role in the impairment of disease-related quality of life (QOL). Based on a survey of 1,000 PD patients, classic motor disability was responsible for merely 17% of variance in the impairment of QOL, whereas depression was the major contributor to the worsening of QOL. 2 The spectrum of nonmotor manifestations of PD is broad as, detailed in Table 1. This article focuses on depression, sleep, and autonomic dysfunction in PD. Other sections of this supplement review dementia, impulse control disorders, and olfactory dysfunction in PD. Depression in Parkinson’s Disease Epidemiology The reported prevalence rates of depression in PD range from 4 to 76%. 3,4 The wide variation is attributed to inconsistency in study methodologies, including differences in sampling procedures, choice of diag