 The investigators propose to test the hypothesis that the sympathetic nervous system contributes to the cardiovascular and inflammatory abnormalities present in the chronic fatigue syndrome CFS and, in particular in the subset of patients characterized by postural tachycardia syndrome POTS. CFS and POTS are seen mostly in otherwise normal young women, and are the cause of significant disability. A substantial proportion of patients referred for evaluation of POTS met diagnostic criteria for CFS and, conversely, a subset of patients referred for treatment for CFS have POTS. The investigators hypothesize that sympathetic activation underlies the pathophysiology of patients in whom CFS and POTS overlap CFS-P. 