Effects of chloroquine on gastric and bile secretion in rabbits were studied by intravenous injection of the drug. Furthermore the excretion rate of the drug into gastric juice and bile was determined. 1) Using the continuous collection technique, the basal secretory rate of gastric juice was found to decrease gradually with the lapse of time. However doses of 5 and 10 mg/kg of chloroquine, when injected intravenously, showed down the basal secretory rate. 2) On the other hand, these doses of the drug caused an elevation of gastric free acidity, and this stimulant effect on the acid secretion was more notable in the dose of 10 mg/kg, lasting for 3 hours after the intravenous injection. 3) Following intravenous injection of 10 mg/kg of chloroquine the drug was found to be excreted into gastric juice, yielding the concentration of 32.4～81.0γ/l after 20 minutes and reaching the maximum of 659.8～792.0γ/l after 3 hours. This concentration tended decrease after 4 hours. 4) Intravenous injection of chloroquine showed no effect on bile secretion by the same continuous collection technique. 5) The dose of 10 mg/kg of the drug was injected intravenously and it was shown that the drug was excreted also into bile. The concentration curves rose rapidly to the maximum of 531.1γ/l 1 hour after the injection and slowly returned to the level of about 40% of the maximum after 4 hours. 6) These results show chloroquine has a stimulant action on gastric secretion, particularly on gastric acid secretion, but has no significant effect on bile secretion in the doses administered.