The purpose of this study was to evaluate the effect of xylooligosaccharide (XOS) on the blood sugar, lipids and oxidative status in type 2 diabetes mellitus (DM). A total of 26 outpatient subjects of Taichung Veterans General Hospital, Taiwan, with HbA1c levels between 7.0 and 10.0% and triglyceride <400 mg/dL were enrolled in the present study. Subjects were supplemented with 4 g/d XOS (n=12) or a placebo (n=14) for 8 wk in a randomized double-blind clinical design. The results showed that the anthropometric values and nutrient intakes did not change during the experimental period. XOS supplementation not only reduced the glucose, HbA1c and fructosamine concentrations, but also decreased the levels of total cholesterol, low density lipoprotein (LDL) cholesterol, oxidized low density lipoprotein (ox-LDL) and apolipoprotein B. The activity of catalase of the erythrocyte sample decreased in the XOS group, but not the activities of superoxide dismutase and glutathione peroxidase. In conclusion, the dietary supplementation with XOS for 8 wk was effective in improving the blood sugar and lipids in type 2 diabetes, indicating that XOS-containing diets might be beneficial to DM subjects.