This proposal will determine: (1) if there is an association between PSP and specific genes of interest; (2) if there is an association between PSP and occupational and/or environmental chemical exposures functionally or structurally similar to known parkinsonian toxicants; and (3) if hypertension or traumatic brain injury prior to symptom-onset is associated with PSP. To disentangle the complex etiology of PSP, this case-control multicenter study involves 500 PSP cases, 500 age/gender matched primary controls, and 500 secondary controls for genetic confirmation. Understanding the etiology of PSP may also help explain the causes of other related diseases such as Alzheimer's disease. This multidisciplinary team of movement disorder specialists, epidemiologists, geneticists, biostatisticians, industrial hygienist and toxicologist is well suited to unravel the etiology of PSP.