Aim To observe the changes of plasma oxidized low density lipoprotein (OLDL)levels of experimental atherosclerotic rabbits with or without polysaccharide krestin(PSK)treatment.Methods All rabbits were fed standard chow supplemented with 1% cholesterol and 4% lard for 12weeks,then injected introperitoneally with 2.5% PSK (or saline)3.5 ml.Plasma levels of OLDL were measured by HOL2 and HOL5 monoclonal antibodies using ELISA method at 0,4,8 and 12 week after treatment.The atherosclerotic lesion areas were determined by computer.Results We found that there is positive correlation between plasma OLDL levels and the area of atherosclerotic plaque of atherosclerotic rabbits both in PSK treated group and in control group,detected either by HOL2 or by HOL5.Moreover,striking decrease of plasma leves after PSK treatment was found and there was signif cant decrease between two groups at 8 and 12 week(P<0.01 )Conclusions The results suggested that OLDL level in plasma detected by monoclonal antibodies is a good index to reflect the degree of atherosclerotic lesion.Furthermore,by using monoclonal antibodies,we present direct evidence that PSK can decrease plasma OLDL levels,espesially highly oxidized LDL, and find this effect is in accordance with the decrease of atherosclerotic plaque area.