The autonomic nervous system has a central role in the regulation of blood pressure. Primary Autonomic Failure is manifested in a variety of syndromes. Orthostatic hypotension is a usual presenting symptom. Primary Autonomic Failure may be the primary diagnosis, and classifications include pure autonomic failure (PAF), also called idiopathic orthostatic hypotension (Bradbury-Eggleston syndrome) autonomic failure with multiple system atrophy (Shy-Drager syndrome) and also Parkinson's disease. Regardless of the primary condition, autonomic dysfunction underlies orthostatic hypotension.