This study was conducted to investigate the effect of soyligosaccharides on improvement of diabetes mellitus. Sprague Dawley rats were divided into three groups. Control and one experimental group were fel AIN-93G diet(mixed diet) and the other experimental group was fed a similar diet containing 5% soyligosaccharides(oligosaccharide diet) for 6 weeks. Experimental groups were divided into two sub-groups after streptozotocin(STZ) injection and fed th mixed diet or the oligosaccharide diet for the next 2 weeks. Followings are final experimental and control groups: MM (mixed dietlongrightarrowSTZ injectionlongrightarrowmixed diet). MO(mixed dietlongrightarrowSTZ injectionlongrightarrowoligosaccharide diet), OM( oligosaccharide dietlongrightarrowSTZ injectionlongrightarrowmixed diet), OO(oligosaccharide dietlongrightarrowSTZ injectionlongrightarrowoligosaccharide diet), C(mixed dietlongrightarrowplacebo injectionlongrightarrowmixed diet). Blood glucose was analyzed at d1, d8 and d12 after streptozotocin injection. At the end of the experimental period, fecal bifidobacteria, plasma insulin, total lipid, triglyceride, cholesterol, and leptin concentrations was analyzed, After STZ injection, blood glucose level was significantly elevated in experimental group compared to a control group. Elevated blood glucose level declined faster in OO group compared to the other experimental groups. Meanwhile, insulin concentration decreased in all experimental groups compared to a control group. The number of bifidobacteria was significantly increased in oligosaccharide diet groups after STZ injection (MO and OO) than a mixed diet group(MM). Plasma cholesterol concentration significantly decreased in oligosaccharide diet groups(MO and OO) compared to mixed diet groups (MM and OM) after SZ injection. Plasma triglyceride and liver cholesterol concentrations significantly decreased in MO group compared to other experimental groups. Meanwhile, plasma leptin concentration was significantly lower in oligosaccharide diet groups after STZ injection(MO and OO) compared to a control group. The results in this study suggest that the dietary soyoligosaccharides has strong on reduction of reduction of blood glucose and lipid concentrations in streptozotoicin-induced diabetic rats. Thus, the use of soyoligosaccharides at a diet for IDDM patients may help to improve diabetes mellitus symptoms.(Korean J Nutrition 34(1) : 3-13, 2001)