Norepinephrine concentration and dopamine-beta-hydroxylase activity were measured in the plasma of 10 dysautonomic patients and 10 normal subjects while they were reclining, standing and exercising. While reclining, dysautonomic patients had normal norepinephrine concentrations and blood pressure, but after standing they did not have a normal increase in their levels of norepinephrine (P less than 0.005), dopamine-beta-hydroxylase (P less than 0.05) or plasma protein concentration (P less than 0.01); they became hypotensive. In reclining dysautonomic patients there appeared to be a correlation between blood pressure and plasma norepinephrine concentration. These data support the view that hypertension and hypotension in dysautonomia are related to the rate of norepinephrine release.