This study was performed to investigate the effects of dried powders and water extracts of Paecilomyces tenuipes(P. tenuipes) and Cordyceps militaris(C. militaris) on lipid metabolism, lipid peroxidation and antioxidative capacity and immune status in rats. Thirty-five male Sprague-Dawley rats weighting 195$pm$21g were grouped into five according to body weight. Ratw were raised for four weeks with diet containing either 4%, 2%(w/w) of dried P. tenuipes powders(TP-4, TP-2) or water extracts from equal amounts of each 4% P. tenuipes and C. militaris powder(TE-4, ME-4). Food intake, weight gain of all groups were not significantly different from those of control group. Lipid metabolism in general was not significantly different among all the groups. However both dried P. tenuipes powder lowered plasma cholesterol level slightly, water extract groups showed tendency of higher plasma HDL-cholesterol and lower liver cholesterol levels than control. Plasma and liver thiobarbituric acid reactive substance(TBARS) concentrations of all the experimental groups were lower than control group. Red blood cell(RBC) and liver superoxide dismutase(SOD) activities were not generally different among all groups. Liver xanthine oxidase(XOD) activities of all groups were tended to be lower than control group. Proliferation of aplenocytes induced by mitogens, concanavalin A and lipopolysaccharide, were increased in TP-2 group. The TP-4 group showed increased CD8 T cells and MHC class II expression without changes in CD4 T cells, B cells and G/M ratio, suggesting activated cytotoxic T cell activity in vivo. Increase of G/M ratio but not of MHC class II in TP-2 group indicated the possible acute inflammatory reaction by the ingested substances in gastrointestinal tract. ME-4 group showed enhanced cellular immunity without vigorous changes of immune parameters in brief periods. In conclusion, both P. tenuipes and C. militaris stimulated antioxidant capacity and immune status in rats. Among groups, water extract of C. militaris was most effective in both capacities, though dried powder of P. tenuipes at 2% dietary level was more effective in antioxidant activity, as various results by different strains were observed.(Korean J Nutrition 34(3) : 271~284, 2001)