The poly (ADP-ribose) polymerase (pADPRp) was found to be involved in DNA repair, DNA replication and recombination etc. There were several reports suggesting the involvement of pADPRp in apoptosis process, but only in limited conditions. To study the function of pADPRp in the apoptosis induced by alkylating agent or by cytotoxic lymphocyte, various cells were treated with a pADPRp in the apoptosis induced by alkylating agent or by cytotoxic lymphocyte, various cells were treated with a pADPRp inhibitor, 3-aminobenzamide (3-AB), as well as mitomycin C (MMC) or cytotoxic lymphocyte. P815 mouse mastocytoma, A20 B cell lymphoma and HL-60 human promyelocytic cells treated with MMC or cytotoxic lymphocyte showed DNA ladder of multiple nucleosomal sizes. DNA fragmentation induced by MMC was gradually decreased by increasing dose of 3-AB in HL-60 cells, but not in other cells. This result suggest that apoptosis signaling pathway in HL-60 cell, which is deficient in p53 expression, involves pADPRp, but not in others. The DNA fragmentation induced by cytotoxic lymphocyte was not affected by 3-AB in all the three cell types, suggesting that the apoptosis signaling pathway by MMC is different from that by cytotoxic lymphocyte.