We have investigated the effects of 1,8-cineole [the main component of essential oil prepared from bay-leaves Laurus nobilis L.)] on DNA of human leukemia cell lines, Molt 4B, HL-60 and stomach cancer KATO III cells. Specific induction of apoptosis by 1,8-cineole was observed in human leukemia Molt 4B and HL-60 cells, but not in human stomach cancer KATO III cells. Morphological changes showing apoptotic bodies were observed in the human leukemia HL-60 cells treated with 1,8-cineole. The fragmentations of DNA by cineole to oligonucleosomal-sized fragments that is a characteristic of apoptosis were concentration- and time-dependent in Molt 4B and HL-60 cells, but not in KATO III cells. The present study shows that the suppression growth by 1,8-cineole in the leukemia cell lines results from the induction of apoptosis by this compound.