Because most type-2 Diabetes Mellitus(DM) is a consequence of both impaired insulin secretion and insulin resistance, it should be treated most efficiently using insulin and thiazolidinedione(TZD), a novel insulin-sensitizer, in combination. In our study, patients with non-obese type-2 DM treated with insulin alone were further administered with TZD. In 80% of patients, addition of TZD caused not only the decrease in insulin dosage and/or HbA1c but also the decrease in hypoglycemic events presumably through improvement in insulin profile, i.e. endogenous:exogenous ratio. More importantly, TZD did not cause unfavorable increase in BMI and patients positively accepted these changes. We conclude that combination of TZD and insulin is a good regimen for non-obese type-2 DM.