We established two novel PH-positive acute leukemia cell lines with "biphenotypic" feature, NALM-27 and NALM-28, with t(9;22;10)(q34;q11;q22) from a patient with biphenotypic acute leukemia(BAL). The breakpoint cluster region (bcr) of the BCR gene was found to be rearranged in these cells by Southern blot analysis using a major 3'-side bcr probe. Polymerase chain reaction (PCR) results showed differences in the pattern of expression of the abl-bcr fusion gene in comparison with the diagnosis. In the case of variant Ph translocations, reports have appeared concerning mainly chronic myelogenous leukemia (CML), but there have been few concerning acute leukemia with lymphoid feature. This study thus identifies nonrandomly involved chromosome sites which can then be targeted for detailed molecular analysis to obtain an understanding of abl-bcr fusion in the cells with lymphoid feature. In addition, chromosome band 10q22, involved in this translocation, is the site for several neoplasia. Furthermore, this site is non-randomly involved in the formation of variant Ph translocations in acute lymphoblastic leukemia (ALL). This is the first report on the t(9;22;10)(q34;q11;q22) rearrangement in NALM-27 and NALM-28 cell lines which should prove useful for understanding the translocation of molecular breaks within the bcr of the complex translocation site.