The sympathetic nervous system may play a pivotal role in the development of primary (essential) hypertension, and is almost always involved in the increasingly common occurrence of postural hypotension. This report reviews the recent evidence for and against stress-induced activation of sympathetic activity leading to a hyperkinetic circulation as an initiating mechanism for most hypertension. Then, attention is directed to the role of altered sympathetic nervous system responsiveness in the development of postural hypotension. Finally, therapy for this syndrome is reviewed.