Very high blood glucose concentrations were seen in rats one day after injection with alloxan or streptozotocin. Those levels fell (compared to day one, p less than 0.005) by the third day after injection and subsequently rose again during the ensuing days. In contrast, no significant differences between treated and control rats in concentrations of submandibular kallikrein were recorded until the tenth day after the initial injection. At that time the submandibular kallikrein concentrations in the alloxanized and streptozotocinized rats were less (p less than 0.01) than those of the untreated rats. A further fall (compared to day ten, p less than 0.005) took place over the next four days. Thus submandibular kallikrein would not seem to have been involved in the early stages of the experimental diabetes. In agreement with that conclusion were the results of a related series of experiments in which exogenous porcine pancreatic kallikrein was administered to alloxanized rats. The kallikrein did not bring about a reduction in the high blood glucose levels.