CHOP (GADD153) is a member of the C/EBP family and a stress‐induced protein. To investigate the role of CHOP in cellular growth, we expressed CHOP conditionally in M1 myeloblastic leukemia cells that do not express p53 protein. More than 60% of M1 cells died through apoptosis 72 h after CHOP induction. Site‐directed mutagenesis revealed that this process requires leucine zipper domain but neither intact basic region nor trans‐activation domain. CHOP‐mediated apoptosis accompanied downregulation of bcl‐2 mRNA and overexpression of Bcl‐2 delayed the process. Our results indicate that CHOP can induce apoptosis in a p53‐independent manner.