Oat or bean products, rich in water-soluble fiber, have distinct hypocholesterolemic effects in humans. After a control diet, 20 hypercholesterolemic men were randomly allocated to oat-bran or bean supplemented diets for 21 days on a metabolic ward. Control and test diets provided equivalent energy, fat, and cholesterol but test diets had twice more total and 3-fold more soluble fiber. Oat-bran diets decreased serum cholesterol concentrations by 19% (p less than 0.0005) and calculated low-density lipoprotein cholesterol by 23% (p less than 0.0025). Bean diets decreased serum cholesterol concentrations by 19% (p less than 0.0005) and low-density lipoprotein cholesterol by 24% (p less than 0.0005). Oat-bran increased fecal weight by 43% but beans did not. While oat-bran increased fecal bile acid excretion, beans had the opposite effect. Oat-bran or bean supplements may have an important role in nutritional management of selected hypercholesterolemic patients.