 We are studying the effects of oral water ingestion in patients with orthostatic hypotension. This has been termed the Gastropressor Response. In this study, we are testing the null hypothesis that the blood pressure increase with oral water ingestion will not be diminished if a full prior water dose is given a few hours earlier. In this 2 day study, subjects will be asked to drink with 1 oz or 16 oz of water in the morning followed a few hours later by 16 oz water while the blood pressure is monitored. On the 2nd day, the other dose of water will be given to start, with 16 oz again as the second dose. 