In order to investigate the preventive and therapeutic of royal jelly on diabetes, the levels of blood glucose and serum lipids as well as the number of blood cells were determined in streptozotocin(STZ) diabetic rats. Rats were divided into seven groups. The RJ group was administered royal jelly and the STZ group was treated with streptozotocin to induce diabetes. To determine the preventive effect, diabetes was induced after administration of royal jelly for 2 weeks in group RS1/RS2. In group SR1/SR2 diabetic rats were administered royal jelly for 2 weeks to investigate the therapeutic effect. After 3 weeks, the body weight was reduced in STZ and SR1 groups and food intake was increased in the STZ, RS1 and SR1 groups. The blood glucose level was similar to the control group in the RJ, RS1 and RS2 groups and there was no effect in the other groups. The total lipid and triglyceride level were lower in the SR1 group as compared to STZ, and the total cholesterol level was higher in the STZ group. The index of atherogenesis was lower in the RJ and SR1 groups compared to the normal group. The number of red blood cells and hemoglobin was higher in the RJ and SR1 groups and the number of white blood cells was higher in the RJ and SR2 groups.