A novel human leukaemia cell line (Kasumi-4) was established from the peripheral blood of a 6-year-old girl suffering from chronic myelogenous leukaemia (CML) in blast crisis. The Kasumi-4 cells had the following characteristic features: undifferentiated blasts which were positive from CD34, CD33 and CD13 surface markers, but negative for myeloperoxidase platelet peroxidase, CD36, CD41 and CD42; chromosome abnormalities of t(9;22;11) (q34;q11;q13), inv(3)(q21q26); and elevated expression of EVI1 gene which is located at chromosome band 3q26. Megakaryocytic maturation was not observed in the liquid culture following the addition of TPA, IL3, IL-6 or GM-CSF, b2-a2 type of BCR-ABL chimaeric messenger RNA was detected by RT-PCR analysis. This the first leukaemia cell line with a three-way translocation containing the the Ph chromosome and the second cell line with an inv(3)(q21q26). This cell line appears to be useful for studying the mechanisms of leukaemogenesis involving these chromosomal abnormalities and related oncogenes.