The effects of chitin and chitosan on the contents of plasma and liver lipids and the fecal excretion of neutral and acidic steroids were investigated in rats fed with atherogenic diet. Dietary chitin did not affect plasma total cholesterol, LDL cholesterol and HDL cholesterol, while chitosan diet de creased total cholesterol and LDL cholesterol. Plasma content of triglyceride was reduced signif icantly by chitin diet but not by chitosan. Increases in fecal weight were observed in rats fed with either chitin or chitosan, and the increase was greater with chitosan than with chitin. Dietary chitosan resulted in an increase of fecal excretion of neutral steroids without any changes in the excretion of acidic sterols. Putting the results together, dietary chitosan reduces plasma cholesterol probably due to the reduction of cholesterol absorption. The decrease in plasma triglyceride level by dietary chitin requires further research to understand the mechinism.