The clinical efficacy of bezafibrate was examined with special reference to glucose metabolism in patients with type 2 diabetes mellitus (DM2). In protocol 1, 342 patients with DM2 and hyperlipidemias were randomly divided into 2 groups, 16-week bezafibrate treatment (n = 174) and no bezafibrate treatment (n = 168). In protocol 2, 20 DM2 patients were randomly divided into 2 groups, 8-week bezafibrate treatment (n = 10) and no bezafibrate treatment (n = 10), and a meal tolerance test (MTT) was performed. In protocol 1, bezafibrate treatment significantly reduced the fasting levels of triglyceride (TG) by 50% +/- 1.6%, total cholesterol (TC) by 12% +/- 1.1%, plasma glucose (PG) from 151.3 +/- 3.5 to 128.6 +/- 3.4 mg/dL, and hemoglobin A1c (HbA1c) from 7.2% +/- 0.1% to 6.9% +/- 0.1%, and significantly increased high-density lipoprotein cholesterol (HDL-C) by 20% +/- 0.8%. In protocol 2, fasting TG, PG, and insulin levels were significantly reduced by bezafibrate treatment. Moreover, in the MTT, postprandial increments of TG were significantly blunted after bezafibrate treatment, whereas postprandial PG and insulin levels were not significantly changed. Leptin levels were significantly decreased, while tumor necrosis factor alpha (TNF-alpha) levels were not changed. In conclusion, both hyperglycemia and hyperlipidemia can be improved by bezafibrate treatment in DM2.