Alloxan is a well known diabetogenic agent which destroys the beta-cell of the Langerhan s islet. The authors investigated the influence of the repeated infusion of glucose solution upon the toxicity of alloxan in the mice. The effects of glucose on the blood sugar content and the serum transaminase (S-GOT and S-GPT) activities in the rabbits treated with alloxan were also observed. The results were as follows: 1. The LD<sub>50</sub> of alloxan in mice showed a slight decrease by pretreatment with glucose for one or two weeks. 2. The elevated blood sugar level in rabbits induced by alloxan shelved a significant fall for the first 3 days by pretreatment with glucose. 3. The increased serum transaminase activities in rabbits induced by alloxan decreased for the first 3 days by pretreatment with glucose.