The baroreflex is responsible for maintaining a stable blood pressure (BP) despite changes in body position.1 Standing up results in a reduction in venous return to the heart. Baroreceptors are unloaded, and the baroreflex, by adjusting the heart rate (HR) (vagal component) and total peripheral resistance (sympathetic adrenergic component), prevents a change in BP.2 Neurologic diseases, such as multiple system atrophy, pure autonomic failure, or the autonomic neuropathies, result in lesions of the baroreflex, causing baroreflex failure. There is ensuing orthostatic hypotension (OH), supine hypertension, and loss of diurnal variation in BP.3 Baroreflex sensitivity (BRS) is widely used to quantify the vagal component of the reflex. However, in disorders such as the autonomic neuropathies, the adrenergic component can be differentially or selectively changed.3 Evaluating adrenergic function requires microneurography,2 a method that is too invasive and time-consuming for routine clinical use. An index of the adrenergic component of the baroreflex, the BP recovery time (PRT), has been recently described.4 In the present study, we describe a more complete method that relates PRT to the preceding BP decrease that drives PRT, hence generating an index of adrenergic baroreflex sensitivity (BRS_a/BRS_a1). In addition, to validate the method, we related this index against directly recorded muscle sympathetic nerve activity (MSNA) obtained with microneurographic recordings during the Valsalva maneuver (VM). These discharges selectively regulate the adrenergic pressor response. We then separately evaluated vagal BRS (BRS_v), BRS_a, BRS_a1, and their products (global BRS or BRS_g/BRS_g1), which provides an index of overall BRS on control subjects and patients with increasing severity of autonomic adrenergic failure.