The purpose of this study was to investigate the effects of Natto supplementation on lipid metabolism in rats. Male rats were fed on casein(CON group), steamed soybean(SS group), conventional Natto(N-1 group), garlic(2%) added Natto(N-2 group), red pepper oleoresin(0.2%) added Natto(N-3 group) and galic(2%) and red pepper oleoresin(0.2%) added Natto(N-4 group) as a protein source for 4 weeks. Serum and liver cholesterol levels were significantly lower in the experimental groups than in the control group. Especially, dietary N-2, N-3 and N-4, compared with CON, reduced markedly the concentration of serum cholesterol. The concentration of serum HDL-cholesterol was higher markedly in the N-4 group than in the control group. The concentration of serum triglyceride was significantly lower in the N-1, N-2, N-3 and N-4 groups than in the control group. Garlic and red pepper added Natto fed groups(N-2, N-3, N-4) showed more excreion of fecal bile acid when compared with those values of casein fed group. The results indicate that spice added Natto supplementation may have more beneficial roles in lipid metabolism through reduced cholesterol levels and increased fecal bile acid excretion.