To investigate the mechanism involved in the apoptosis of human monocyte cell line U937 induced by oxidized low density lipoprotein (ox-LDL).The increase of the degree of cell apoptosis was concentration dependent. The apoptotic cells were detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling(TUNEL),flow cytometry and DNA fragment analysis. The protein contents of c-fos，c-jun and c-myc were analyzed by immunochemical staining. The expression of c-fos，c-jun and c-myc mRNA were quantified by reverse transcription-polymerase chain reaction (RT-PCR).The results show that ox-LDL could upregulate the gene expression of c-fos，c-jun and c-myc, which induced the apoptosis of U937 cells.