The acute lymphoblastic cell lines designated BAL-KHc and BAL-KHs were established from the peripheral blood of a Japanese female patient with a B-cell acute lymphoblastic leukemia. The BAL-KHc and BAL-KHs exhibited B-cell characteristics with positive cell markers for CD19, CD20, CD21 and HLA-DR antigens. Immunoglobulin with gamma and kappa chains was demonstrated on the cultured and fresh leukemia cells respectively. The cells lacked the Epstein-Barr virus genome and expressed abnormal chromosome constitutions including a t(8;14)(q24;q32). These results suggested that the cell lines present B-cell characteristics. The BAL-KHc cells showed different cell growth characteristics and cell surface marker profile compared to those of the BAL-KHs. These variations suggest that the BAL-KHc cells were probably frozen at a different stage of B-cell maturation from those of BAL-KHs, although both cell lines originated from the cells in the same peripheral blood sample of the patient.