To test the hypocholesterolemic mechanisms of corn husk oil (CoHO), male Hartley guinea pigs were fed diets containing increasing doses of CoHO, either 0 (control), 5, 10, or 15 g/100 g, and 0.25 g/100 g cholesterol. A positive control group (LC) with low dietary cholesterol (0.04 g/100 g) was also included. Fat was adjusted to 15 g/100 g in all diets by the addition of regular corn oil. Plasma low density lipoprotein (LDL) cholesterol concentrations were 32, 55, and 57% (P < 0.0005) lower with increasing doses of CoHO. In addition, intake of CoHO resulted in 32 to 43% lower hepatic total and esterified cholesterol and 55 to 60% lower triacylglycerol concentrations compared with the control group (P < 0.01). CoHO intake resulted in plasma and hepatic cholesterol concentrations similar to those in guinea pigs from the LC group. The number of cholesteryl ester and free cholesterol molecules was higher in LDL from the control group than in LDL from the CoHO or the LC groups. Hepatic beta-hydroxy-beta-methylglutaryl-coenzyme A reductase activity was not modified by CoHO intake whereas cholesterol 7alpha-hydroxylase was up-regulated by 45 to 49% (P < 0.01) in the 10 and 15 g/100 g CoHO groups. Hepatic acyl coenzyme A cholesterol acyltransferase activity was down-regulated in a dose-dependent manner by 54, 58, and 63% with increasing doses of CoHO. CoHO intake resulted in increased fecal cholesterol excretion by 40 to 55% compared with the control and LC groups. Total fecal neutral sterol excretion was enhanced 42 to 55% by CoHO compared with the control group and by 59 to 68% compared with the LC group. The data from these studies suggest that CoHO has its hypocholesterolemic effect by decreasing cholesterol absorption and increasing bile acid output. These alterations in the intestinal lumen alter hepatic cholesterol metabolism and may affect the synthesis and catabolism of lipoproteins.