Primary lymphomatous effusions are represented by cases of non-Hodgkin's lymphoma (NHL) which grow in liquid phase in the serous body cavities in the absence of solid tumour masses. Based on morphologic, immunophenotypic, virologic and genotypic features, primary lymphomatous effusions are distinguished into body cavity-based lymphoma (BCBL), Burkitt's lymphoma (BL) and immunoblastic large-cell lymphoma. The histogenesis and pathogenesis of primary lymphomatous effusions are virtually unclarified. In this study, we have established 2 cell lines (CRO-AP/1 and CRO-AP/2) representative of 2 distinct categories of primary lymphomatous effusion, BCBL (CRO-AP/2) and BL (CRO-AP/1). Both CRO-AP/1 and CRO-AP/2 carry monoclonal re-arrangements of the immunoglobulin genes which are identical to those of the respective parental tumours. Consistent with its BCBL origin, CRO-AP/2 is characterised by a non-B, non-T phenotype and harbours infection by HHV-8 (approx. 100 viral copies/cell) and Epstein-Barr virus. Conversely, CRO-AP/1 expresses several B cell-associated antigens, lacks HHV-8 infection and carries the genetic hallmark of BL, i.e., a chromosomal breakpoint of band 8q24. CRO-AP/1 and CRO-AP/2 may be valuable for the biologic characterization of primary lymphomatous effusions, particularly since the number of available cell lines derived from such lymphomatous effusions is extremely limited.