AIDS-related non-Hodgkin lymphomas (AIDS-NHL) are most frequently derived from B cells and include small non-cleaved cell lymphoma (SNCCL) and diffuse large cell lymphoma (DLCL) and less frequently anaplastic large cell lymphoma (ALCL) or body cavity-based lymphoma (BCBL). AIDS-NHL cell lines have proved useful to study AIDS-NHL pathogenesis. In this report, we describe the establishment and molecular characterization of two novel AIDS-NHL cell lines (HBL-4 and HBL-6) derived from lymphomatous effusions. HBL-4 was derived from a patient with SNCCL, whereas HBL-6 was derived from a patient with BCBL. The identity of the cell lines with the original tumor clone was established by immunoglobulin gene rearrangement analysis. Both HBL-4 and HBL-6 carry a monoclonal EBV infection and do not contain HIV. In addition, HBL-6 harbors DNA sequences of the recently identified Kaposi's sarcoma-associated herpesvirus (KSHV), now formally called human herpesvirus 8 (HHV8). Finally, HBL-4, but not HBL-6, harbors a rearranged c-MYC allele, while the BCL-6 gene displayed a germline configurations in both cell lines. These AIDS-NHL cell lines may prove useful in understanding the biologic events contributing to AIDS-NHL development.