We have previously demonstrated that three potent iron chelators, hinokitiol, dithizone and deferoxamine, induce differentiation of F9 embryonal carcinoma cells, as do other wellโknown morphogens such as retinoic acid (RA) and sodium butyrate (NaB). In this study, we compared the patterns of cell proliferation, cell death and cell cycle arrest during the process of differentiation induced by these five agents. When F9 cells were cultured with the agents at their individual differentiationโinducing concentrations, cell proliferation was rapidly inhibited by treatment with the iron chelators and NaB. In contrast, RA did not influence the rate of increase of cell number at the concentration of 1 ฮผm. The three chelators also caused a marked reduction in cell viability, and the treated cells exhibited internucleosomal DNA fragmentation, whereas cells treated with NaB showed no apoptotic characteristics. RA induced apoptosis weakly at 1ฮผm and strongly at higher concentrations. In addition, all the iron chelators hindered cell cycle progression, resulting in an arrest at the G1โS interface or S phase. The phenomena observed in chelatorโtreated cells were considerably different from those in RAโ or NaBโtreated cells. It is concluded that the three iron chelators cause both severe apoptotic cell death and cell cycle arrest of proliferating F9 cells via cellular iron deprivation, and that this apoptotic change may be independent of the process of differentiation.