A lymphoblastoid cell line (SD-1) has been established by Epstein-Barr virus immortalisation of Philadelphia chromosome positive acute lymphoblastic leukaemia (ALL) cells. Using newly derived anti-bcr monoclonal and anti-abl polyclonal antibodies it was demonstrated that both the original leukaemic cells and the derived cell line expressed the p190 form of the bcr-abl protein found in a proportion of cases of Philadelphia chromosome positive ALL. Interestingly, the leukaemia and the derived cell line each displayed different, clonal patterns of immunoglobulin gene rearrangements providing direct evidence that the t(9;22) translocation which results in the expression of the p190 bcr-abl protein must occur before immunoglobulin heavy chain gene rearrangement. In contrast to the leukaemia, which had multiple chromosome abnormalities in addition to the t(9;22), the cell line had the t(9;22) translocation as its sole abnormality. Although SD-1 cells were demonstrated to express continuously the p190 bcr-abl protein, they were unable to form colonies in soft agar and did not cause tumours in splenectomised nude mice. This cell line therefore represents an appropriate target cell line in which to examine the cooperativity of the p190 bcr-abl protein with other activated oncogene products.