Background: Ingestion of about half a liter of plain water raises blood pressure in a few minutes in patients with autonomic failure [1], probably due to elicitation of a sympathetic reflex [2]. In healthy individuals, this pressor response of plain water ingestion is disputed [3,4]. Other types of fluid, such as isotonic banana juice, could have different effects [5]. Materials and Methods: In a cross-over experimental study, young medical students ingested 500 mL of plain water (PW), 500 mL of oral rehydration solution (ORS) or 400 mL of fruit juice (FJ) on separate occasions, at least two days apart. Their heart rate (HR, bpm) and blood pressure (BP, mmHg: systolic, SBP and diastolic, DBP) were recorded immediately after (0 min), and at 2, 5, 20 and 40 min after fluid ingestion and compared with initial (pre-ingestion) values (ANOVA repeated measures). Results: Sixty nine apparently healthy students (40 males, 29 females; aged 18-24 years) participated. Compared to initial values, SBP and DBP were significantly (p=0.000) with ORS and FJ ingestion at 0, 2 and 5 min; then lowered at 20 and 40 min (fig. 1). With PW, the BP changes were not significant at time of measurement (p>0.1). In all three experimental set ups, HR increased significantly (p=0.000) at 0, 2 and 5 min and lowered to near initial levels then after (fig. 2) Conclusion: Ingestion of ORS (500 mL) and FJ (400 mL), but not PW (500 mL), is associated with acute rises in BP in healthy young adults. This finding could have implications on the choice of fluid for prophylaxis in hypotensive conditions such as blood donation, postural hypotension, and autonomic dysfunction.