We established and characterized a new acute lymphoblastic leukemia (ALL-L3 according to FAB classification, or Burkitt's type) cell line, KHM-10B. The morphology of the patient's lymphoblasts and KHM-10B cells corresponded to that of ALL-L3 cells. The cells were positive for HLA-DR, CD19 and surface immunoglobulin (mu, lambda). Southern blot analysis revealed that the fresh lymphoblasts and KHM-10B shared the same immunoglobulin gene rearrangement. Conventional cytogenetic analysis of fresh lymphoblasts from the patient and KHM-10B cells revealed the 13q34 abnormality, the second most common additional abnormality in Burkitt's lymphoma, but no detectable 8q24 involvement. Rearrangement of the c-myc oncogene was not detected by Southern blot analysis. However, a fluorescence in situ hybridization (FISH) assay identified a t(8;22)(q24;q11). The KHM-10B cells were arrested at S phase with hydroxyurea and thymidine, and the synchronized cells progressed through the cell cycle in drug-free medium. The expression of c-myc and max was observed throughout the cell cycle, as was found in the Burkitt's lymphoma cell in Raji. Our findings indicate that FISH analysis is of diagnostic value in detecting obscure chromosomal translocations and that max, as well as c-myc, is expressed constitutively in ALL-L3 and Burkitt's lymphoma cell lines.