The arterial blood pressure (BP) components of the Valsalva maneuver (VM) were analyzed to ascertain whether they could be used as an index of adrenergic regulation of the circulation. We studied a control and three age- and sex-matched patient groups. Sympathetic adrenergic failure was graded on the basis of the degree of systolic BP (SBP) reduction during tilt: orthostatic hypotension (OH; SBP greater than 30 mmHg), borderline OH (BOH; 30 less than SBP greater than 10 mmHg), and sympathetic sudomotor failure (SSF). Controls exhibited a biphasic phase II, consisting of a modest decrement (early phase II) followed by a rise in BP (late phase II; II1) above resting values. All the patient groups including SSF exhibited a significant reduction in II1. An excessive BP fall in phase II and an absent phase IV overshoot were observed in the OH group. BOH and, to a lesser extent, SSF groups showed a significant reduction in phase IV overshoot. We conclude that BP changes during VM will detect adrenergic vasoconstrictor failure with greater sensitivity than orthostatic BP recordings.