A new human lymphoma cell line, designated DL-40, was established from the peripheral blood of a 64-year-old woman with leukemic conversion of aggressive large cell lymphoma. The cell line grew in suspension with or without forming clumps of cells and exhibited large, round, or multiple nuclei in the relatively abundant cytoplasm that was positive for acid phosphatase. The cells expressed a Ki-1 antigen (CD30), E+, CD2+, CD4+, CD45+, Ia+ phenotype and had rearranged T-cell receptor beta chain but were negative for CD15, HTLV-I, and Epstein-Barr virus nuclear antigen. Chromosome analysis of this cell line showed a human female karyotype with complex hyperdiploid abnormalities. DL-40 cells produced tumors histologically similar to the original lymphoma when transplanted into nude mice and immunosuppressed hamsters. The DL-40 cell line could provide a useful tool for the understanding of biology of the Ki-1-positive non-Hodgkin's lymphoma.