Cytokines, particularly interleukin 1 (IL-1) and tumor necrosis factor, are known to induce hypoglycemia in normal rodents or different experimental models of type II diabetes. We investigated, at the pre-diabetic stage, the effect of short-term administration of murine recombinant interleukin-1α (mrIL-1α) on the levels of glucose, insulin and corticosterone in the non-obese diabetic (NOD) mouse, a spontaneous model of type I diabetes. Two-month-old, pre-diabetic NOD mice of both sexes were insensitive to mrIL-1α (12·5 and 50 μg/kg) 2 h after administration, the time at which the maximal decrease (around 50%) was observed in the C57BL/6 mouse strain. Kinetic studies however showed that mrIL-1α lowered glycemia in both sexes of NOD mice, but the effect was limited and delayed. In the NOD and C57BL/6 strains, mrIL-1α had no influence on insulin levels in females, but significantly increased them in males (P<0·0001). Castration of NOD males abrogated the stimulatory effect of mrIL-1α on insulin secretion. Corticosterone secretion was stimulated by mrIL-1α in both sexes of NOD and C57BL/6 mice, and this effect was faster and greater in NOD females than in C57BL/6 females. The incomplete hypoglycemic response to mrIL-1α in females may be attributed to the anti-insulin effect of glucocorticoids, an effect which can be demonstrated when mrIL-1α is administered to adrenalectomized animals or when mrIL-1α is administered together with the glucocorticoid antagonist RU38486. In NOD males, in contrast, glucocorticoids did not play a major role in the limited hypoglycemic response to mrIL-1α, since RU38486 and adrenalectomy were not able to unmask a hypoglycemic effect. Moreover, NOD mice of both sexes were less sensitive than C57BL/6 mice to the hypoglycemic effect of insulin (2·5 U/kg), which suggests some degree of insulin-resistance in NOD mice. With regard to the effect of IL-1 on NOD mouse glycemia, therefore, these results suggest that glucocorticoids and/or androgens, according to the animal's sex, may induce a state of insulin-resistance.