In order to evaluate the specificity of alkyl-lysophospholipid-induced cell destruction, peripheral blood leukocytes from chronic myelogenous leukemia (CML) patients in chronic phase of the disease as well as in blastic crisis have been separated by density centrifugation. These subpopulations, enriched for the different maturation stages, were tested for their sensitivity to alkyl-lysophospholipids. It is shown that myelocytes in chronic phase CML are resistant, but blast cells from both clinical stages as well as maturational defective myelocytes from blastic crisis CML are highly sensitive to these antimetabolites. In contrast to chronic phase CML myelocytes, these sensitive cells show a high lysophospholipid adsorption rate and lack an O-alkyl-cleavage enzyme.