The effect of a probiotic composed of Bacillus, Lactobacillus, Streptococcus, Saccharomyces and Candida species (each at 107–8 colony-forming units (cfu)/g rice bran), given at a level of 150 g/kg diet for 6 weeks, on lipid metabolism was examined in the faeces, serum and liver of male rats. Liver weight decreased 35% in the rats fed on a high-fat, high-cholesterol diet containing the probiotic. Total cholesterol concentration in the serum was significantly lower in the probiotic group than in the control group throughout the experimental period in rats fed on the high-fat, high-cholesterol diet, and HDL-cholesterol concentration was significantly higher (P < 0·05) in the probiotic group than in the control group which was fed for the 6 week experimental period on a basal diet. The serum VLDL + IDL + LDL cholesterol concentrations in the probiotic groups were reduced compared with those of the corresponding control groups. The probiotic groups fed on the high-fat, high-cholesterol diet and the basal diet had lower hepatic cholesterol concentrations than did the corresponding control groups (P < 0·05). Hydroxymethylglutaryl coenzyme A reductase (NADPH) (EC. 18.104.22.168) activity in the liver was lower in rats fed on the high-fat, high-cholesterol diet with the probiotic. The neutral and acidic steroid concentrations in faeces were higher in the probiotic group than in the control group fed on the high-fat, high-cholesterol diet. Escherichia coli decreased and Bifidobacterium and Eubacterium increased in the faecal microflora of rats fed on the dietary probiotic. Lactobacillus in the probiotic groups was higher than that in the control groups. The present study shows that the probiotic promotes Bifidobacterium and Eubacterium in the faecal microflora, and reduces cholesterol levels in the serum and liver of rats.