The effects of Chlorella regularis powder (CP) and Chlorella regularis indigestible fraction (CIF) on serum and liver lipid concentrations and on fecal steroid excretion were estimated in rats fed diets containing 5 g/kg cholesterol and 2.5 g/kg sodium cholate. The ingestion of 12.7% CP or 5.3% CIF did not influence food intake or growth. CP and CIF decreased the levels of serum cholesterol, but had no effect on the levels of serum triacylglycerol and phospholipid. Liver cholesterol contents were lower in the CP and CIF groups than in the control group, but CP and CIF did not affect liver triacylglycerol content. CP and CIF increased the total amount of fecal neutral steroids excreted, but did not modify the total bile acid excretion. However, the soluble bile acid concentrations of reconstituted fecal water in the rats fed CP and CIF diets were lower than the control value. Moreover, CP and CIF had a high bile acid binding capacity in vitro. These results indicated that CIF had a hypocholesterolemic effect and enhanced fecal neutral steroid excretion while decreasing the soluble fecal bile acid concentration.