Parkinson's disease (PD) is a progressive disorder of the nervous system that affects the motor system. PD results in motor, neuropsychiatric, sensory and sleep diseases. Four cardinal motor symptoms in PD are tremor, postural instability, rigidity and slowness of movement. Neuropsychiatric disturbances such as disorders of mood, behavior, cognition and thought may also occur. An important underlying cause of Parkinson's disease is the death of cells in the substantia nigra, lower levels of dopamine in these regions and the build-up of proteins into Lewy bodies in the neurons. People exposed to certain pesticides and with head injuries in the past are at an increased risk of developing Parkinson's diseases. There is currently no cure for Parkinson's disease. The symptoms can be managed with the help of medications, rehabilitation, surgery and palliative care. This book discusses the fundamentals as well as modern approaches in the study of Parkinson's disease. It aims to shed light on some of the unexplored aspects of PD and the recent researches in this domain. It is a complete source of knowledge on the present status of this important disease.