Clustering of lipid rafts in plasma membranes by hybrid liposomes (HL-23) composed of L-alpha-dimyristoylphosphatidylcholine (DMPC) and polyoxyethylene(23) dodecyl ether (C-12(EO)(23)) for human leukemia HL-60 cells was observed for the first time It was suggested that the induction of apoptosis by HL-23 could be related to an Increase of membrane fluidity and the formation of lipid rafts in the plasma membranes of HL-60 cells