Contribution of Angiotensin II to Supine Hypertension in Autonomic Failure

Inclusion Criteria: * Patients with autonomic failure who exhibit supine hypertension and are in the hospital already participating in the study "The Evaluation and Treatment of Autonomic Failure \[IRB # 000814\] * Supine hypertension, defined as systolic blood pressure \> 150 mm Hg and/or diastolic blood pressure \> 90 mm Hg * Males and females of all races, between 18 to 85 years of age * Able and willing to provide informed consent with the understanding that they may withdraw consent at any time without prejudice to future medical care Exclusion Criteria: * All medical students * Pregnant women * Patients with a history of angioedema * Patients with a known allergy to any ACE inhibitor or angiotensin receptor blocker * High-risk patients \[e.g. heart failure, symptomatic coronary artery disease, liver impairment, history of stroke or myocardial infarction\] * Patients with hemoglobin \< 10.5 \[or hematocrit \< 32\] * Inability to give, or withdraw, informed consent * Other factors which in the investigator's opinion would prevent the patient from completing the protocol including clinically significant abnormalities in clinical, mental or laboratory testing