Intravenous infusion of arginine has been reported to be a powerful stimulus of endogenous gastrin release. This response has been re-examined in 12 normal human subjects. 6 of the subjects showed a 40% or greater rise in serum gastrin, and these responses were widely scattered in time. Changes in overall mean serum gastrin were small and showed a significant (p < 0.05) rise over mean basal levels at only one point in time which was during arginine infusion. In this study arginine infusion resulted in a much smaller and less consistent serum gastrin response than previous reports.