Anti-leukemic T-cell immunoliposomes entrapping cytotoxin from Chinese Cobra(CT)were prepared using dioleoylphosphatidylethanolamine (DOPE ) and monoclonal antibody(McAb)against human pan-T lymphocyte Wu71.The immunoliposomes is pH-sensitive,it is stable in pH7.0～8.0 but easy to release its contents in the slightly acidic environment of target cell plasma,below pH6.0.Treatment of the human T- leukemic cell line CEM with these immunoliposomes and using scanning electron microscopy to observe its dynamic killing action. The result shows that it was highly targetsensitive to the target cells while little cytotoxicity to the human non-target cells.