A novel cell line (KH88) was established from a patient with chronic myelogenous leukemia in blastic crisis. The leukemic blasts had the features of undifferentiated blasts with basophilic agranular cytoplasm and they were focally positive for acid phosphatase and alpha-naphthyl acetate esterase. CD36, CD33, HLADR, and CD71 were expressed on the surfaces of the blast cells. Most blasts were positive for platelet peroxidase activity, and some of them had granules containing aggregates of ferritin molecules. These findings were compatible with those of 'early' erythroblastic leukemia, this established cell line (KH88) having similar characteristics, and actually producing hemoglobin A and hemoglobin F. Although the KH88 cells were negative for megakaryocytic markers, they were induced to express CD41 by phorbol ester. Further, a few KH88 cells were positive for myeloperoxidase. This cell line was thus revealed to have the capacity to differentiate into three lineages, providing a useful model for studying the differentiation of multipotential stem cells. Moreover, a subline of KH88 had a peculiar chromosome abnormality, del(3)(q21q25); it would be useful to study the significance of this chromosomal abnormality.