Aim To investigate which component in oxidized low density lipoprotein(OLDL)is responsible for the apoptosis in macrophages induced by OLDL , the roles of several components in OLDL in apoptosis in macrophages were studied; Methods LDL was modified by Cu2+,cell nuclei were stained with Hoechst 3 325 8 ; DNA ladder was observed by agarose gel electrophoresis。Results OLDL could induce apoptosis in macrophages characterized by appearance of DNA ladder and nucleus condensation , but native LDL and acetylated LDL (Ac-LDL) could not,Pre-clearance of lipid hydroperoxides(LOOH)in OLDL by ebselen plus GSH could partly inhibit apoptosis induced by OLDL. Lipid moiety in OLDL could induce apparent apoptois, but protein moiety could not.BOth linoleic acid and cholesterol, the main components of LDL lipid,oxidized separately,could induce apoptosis in macrophages.The DNA fragmentation induced by linoleic acid and cholesterol oxidized together was much more apparent than that induced by either of linoleic acid and cholesterol oxidized alone.Conclusions LOOH and oxidized cholesterol in OLDL may be responsible for t he apoptosis in macrophages induced by OLDL.