The effects of several factors on the apoptosis of HL-60 cells, a human acute myeloid leukemia cell line, were investigated. The apoptosis model was established with mild heat. Typical changes of cell morphology and characteristic DNA ladder pattern were found. The effect of apoptosis induced by mild heat was enhanced, when HL-60 cells were pretreated with the retinoic acid. By contraries, that of apoptosis was displayed with the slight inhibition while HL-60 cells were pretreated with rhGM-CSF. We also observed the alterations of mRNA expressions of c-myc by the dot hybridization. The results indicate that both the mild heat and the combination of mild heat and retinoic acid obviously reduce the mRNA expression of c-myc compared to the control group.