Bleomycin (BLM) is a commonly used anticancer drug that can generate reactive oxygen species (ROS). BLM is known to cause DNA damage, apoptosis, and cell cycle arrest. We hypothesized that BLM resistance could be caused by suppression of apoptosis and cell cycle arrest, which may be related to adaptation to oxidative stress in BLM-resistant cell lines. We have previously established multiple BLM-resistant cell lines. Among them, SBLM24 and bBLM16 clones had the highest BLM resistance compared to SCC61b cells, a subclone of human oral squamous cell carcinoma (SCC61) cells. The activities of primary antioxidant enzyme in SBLM24 cells, but not bBLM16, was higher than that in SCC61b cells. However, bBLM16 cells had higher increase in coenzyme Q10 levels than SBLM24 cells. In this study, we compared the extent of apoptosis and cell cycle arrest between SCC61b and the two BLM-resistant cells, SBLM24 and bBLM16 cells, after BLM treatment. First, we evaluated the extent of apoptosis by using Hoechst 33342 staining and analysis of sub G1 phase, which represents percentage of apoptotic cells. Results showed that the level of nuclear fragmentation in SCC61b cell was higher than BLM-resistant cells after BLM 48-hr treatment. The increase in percentage of sub-G1 phase in SCC61b cells was greater than that in BLM-resistant cells, especially SBLM24 cells, after 72-hr treatment. Moreover, results of caspases activity assay showed that the extent of caspase-3 and caspase-8 activation induced by BLM was greater in bBLM16 cells than in SCC61b cells, but there was no activation in SBLM24 cells. Furthermore, results of Western blot analysis showed that BLM increased release of cytochrome c and Smac into cytosol and translocation of p53 and Bax into mitochondria in SCC61b cells, but the extent of release or translocation was inhibited in SBLM24 and bBLM16 cells, after 18-hr treatment. BLM also increased proteins levels of both p53 and phospho-p53 (Ser-15) in cytosolic fraction in SCC61b, bBLM16, and SBLM24 cells after 18-hr treatment, but the extent of increase was less in SBLM24 cells. On the other hand, we found that the extent of G2/M arrest by BLM was greater in SCC61b cells than in BLM-resistant cells. Particularly, extent of G2/M arrest in SBLM24 cells was almost completely suppressed. In summary, apoptosis and G2/M arrest induced by BLM in SCC61b cells were almost completely suppressed in SBLM24 cells and partially suppressed in bBLM16 cells. We speculate that the above results could be related to the increase in both antioxidant enzymes and coenzyme Q10 levels in SBLM24 cells and the higher increase of coenzyme Q10 in bBLM16 cells. However, we still need to investigate the mechanisms of suppression of apoptosis and G2/M phase arrest induced by BLM that may not be related to the increase of antioxidant enzyme or coenzyme Q10 in the future.