A study made with six women subjects of the effect of citric acidsodium citrate and sodium bicarbonate on the urinary excretions of citric acid is here reported. The effect on urinary pHtitratable acidityand excretion of total organic acids was also observed. The following results were obtained with chemically equivalent amounts of citric acid and sodium citrate: The increase in pH and the decrease in titratable acidity brought about when sodium bicarbonate was fed were accompanied by a small increase in total organic acids and a considerable increase in citric acid excretion. Increase in total organic acid excretion on ingestion of sodium bicarbonate has been noted in the past, and, more recently, like observations have been made on citric acid excretion. Apparently, citric acid excretion is not dependent upon citric acid ingestion. Increased evidence is presented here for the view that citric acid is one of the organic acids which plays a part in acid-base balance regulation.