This study was designed to clarify the relationship between streptozotocin (STZ) dosage (100, 150 and 200 mg/kg ip) and the resulting diabetogenic response in mice (8-week-old male ICR). In this experiment, we found that a single ip injeciton of 100 mg/kg STZ is able to induce progressive diabetes mellitus, in which non-fasting serum glucose levels begin to rise from 3 weeks and continue to rise throughout the experimental period until 9 weeks. The non-fasting serum insulin levels of 100 mg/kg STZ-treated mice were normal during the experimental period. In addition, the population of insulin-immunoreactive cells (beta cells) in the islets of pancreata was slightly less than in normal mice at 9 weeks. In 200 mg/kg STZ-treated mice, on the other hand, the insulin levels were below measurable values and insulin-immunoreactive cells were not observed. It is concluded from these results that the progressive diabetic mouse model induced by a single ip injection fo 100 mg/kg STZ, unlike 200 mg/kg STZ-induced diabetes which is insulin-dependent, is non-insulin-dependent.