Parkinsonism describes the core clinical criteria of tremor, bradykinesia, rigidity, and postural instability. There is a large differential diagnosis, but the most common cause of parkinsonism is due to Parkinson disease. This review details the epidemiology, etiology/genetics, pathogenesis, diagnosis and differential diagnosis, management, and prognosis of Parkinson disease, dementia with Lewy bodies, progressive supranuclear palsy, corticobasal degeneration, vascular parkinsonism, normal pressure hydrocephalus, and drug-induced parkinsonism. This review contains 8 figures, 32 tables, and 73 references. Keywords: Parkinson disease, parkinsonism, levodopa, cogwheel ridigity, multiple system atrophy, dementia, substantia nigra, palsy, neurodegenerative disease, hydrocephalus, Lewy body, Lewy neurite