AIM: To clarify the relationship between expression of leukocyte iNOS-mRNA and pancreatic islet function in the diabetic rats induced by streptozocin(STZ). METHODS: Wistar rats were randomly divided into the control group ( n =10) and the diabetic group ( n =15). Expression of iNOS-mRNA in the peripheral blood leukocyte, liver and lung were detected with in situ hybridization and the blood sugar and insulin were also measured. RESULTS: It showed that the blood glucose content increased from (8 95?1 80) to (22 84?4 90) mmol?L -1 ,however, the plasma insulin content decreased from (81 76?20 12) to (58 92?18 20) mU?L -1 at the third day after the ? cell was disfunctioned by STZ injection. No expression of leukocyte iNOS-mRNA in normal rat was detected. The percent rate of positive cells were significantly increased in the rats with diabetes. CONCLUSION: The expression of leukocyte iNOS-mRNA is positively related to the damage of ? cells caused by STZ.