Three percent milled-rice was evaluated for beneficial effect on blood glucose level and serum lipid concentrations in an experiment with Otsuka Long-Evans Tokushima Fatty (OLETF) rats, used as model animals for spontaneously non-insulin-dependent diabetes mellitus. The same experiment was carried out using Long-Evans Tokushima Otsuka (LETO) rats, the control of the OLETF rats. The results obtained from the rats given a diet containing 3% milled-rice (3% MRD) ad libitum were compared with those from rats given polished rice. During the feeding period of 140 d, body weight of the OLETF rats receiving the 3% MRD was significantly lower than that of the rats fed on the diet containing polished rice (PRD) from the 48th to the 124th days. The body weight of the LETO rats during the both periods of 90 to 104 d and 114 to 140 d was lower than that of the rats receiving the PRD. Though food intakes of the rats receiving 3% MRD were significantly lower in the OLETF and LETO rats during the two periods of days 48 to 124 and days 1 to 140 than in the rats of the PRD group, the feed efficiency of the OLETF or LETO rats did not show significant difference between the 3% MRD and the PRD groups during the same experimental periods. The excretion rate of feces of the OLETF rats receiving the 3% MRD was significantly higher than that of the rats receiving the PRD, both on the 126th day and during the period of days 129 to 131. The fasting blood glucose levels were significantly lower in the OLETF rats receiving the 3% MRD than the rats receiving the PRD on the 84th day, the 105th day and the 127th day, and also lower in the LETO rats receiving the 3% MRD on the 84th day and the 105th day. The incremental areas under the curve of blood glucose concentrations (IAUC-Glc) for 120 min after oral administration of glucose on the 133rd day was lower in the OLETF rats receiving 3% MRD than that of the PRD. The ratio of IAUC-Glc in the 3% MRD to PRD group, after ingestion of diets for 1 h after fasting for 18 h on the 138th day, was 0.89 in the OLETF rats, and 0.74 in the LETO rats. Compared with the PRD group, the amounts of cholesterol and bile acid in the feces of the OLETF rats in the 3% MRD group were significantly higher on days 129-131, and the cholesterol excretion was significantly higher on the 84th day in the OLETF rats in the 3% MRD group. The liver weight, the level of total lipids in liver, and the concentrations of triglyceride and total cholesterol in liver and serum of the OLETF rats on the 140th day were significantly lower in the 3% MRD than those of the PRD group. These results indicate that 3% milled-rice has beneficial effects on blood glucose level and serum lipid concentrations in spontaneously non-insulin-dependent diabetic rats.