1. In guinea-pigs fed an ascorbic-acid-free diet, as the ascorbic acid levels decreased the histamine levels in blood and urine rose steadily to maxima in about 10-12 days. The elevated histamine levels persisted in the blood and urine of scorbutic guinea-pigs and the histamine levels in lung, gastric mucosa and spleen also increased. The increased histamine content of the urine, blood and other tissues in the ascorbic-acid-depleted condition could be brought back to normal levels by administration of a single dose of ascorbic acid 5 mg/100 g body wt. guinea-pig. 3. The drop in the elevated histamine level was not due to an indirect effect of ascorbic acid on histamine forming capacity, histaminase activity or histamine release.