This is a report of the effects of sugars on salt metabolism and on blood pressure. Twenty young men, none of whom had a personal or family history of hypertension, were orally hydrated after an overnight fast and required to lie recumbent for 6 h except for urinary voiding and blood pressure measurements which were performed at 1/2 h intervals. Venous blood samples were drawn at hourly intervals. The volunteers were kept constantly hydrated by giving them water to drink equivalent to the volumes of urine voided. Two hours from the start of the experiment each subject was given one of the following sugars: glucose, fructose, sucrose, galactose, lactose, or water alone. After oral hydration the subjects appeared to develop natriuresis and kaliuresis. This was quickly abolished by ingestion of either glucose, fructose, sucrose, or lactose, but not by galactose or water alone. Fructose was the most potent antinatriuretic agent. Both glucose and sucrose significantly elevated systolic blood pressure. This lasted for 2 h after glucose ingestion and 1 h after sucrose ingestion.