This study was carried out to explore the hypocholesterolemic effect of dehyulled defatty soy flour and its possible mechanisms including endocrine status, cholesterol biosynthesis, and fecal excretion in rats. Animals fed casein were used as control and each phospholipid compared with casein feeding. Cholesterol concentrations in all lipoprotein fraction were significantly lower in defatted soy flour group compared with casein-fed control. Defatted soy flour feeding also significantly lowered hepatic total lipid, cholesteol and TG, and increaed fecal bile acid excretion by 270% compared with casein feeding. Defattd soy flour feeding had no significant effect on plasma thyroid hormone levels and hepatic 3-hydroxy-3-methyl glutary coenzyme A(HMG-CoA) reductase activity. However, plasma T4 concentration was slightly elevated and HMG-CoA reductase activity was suppressed in defatted soy flour group. These metabolic alterations partially explain the reduced plasma and hepatic cholesterol levels of rats fed defatted soy flour.