The expression of the proto-oncogene bcl-2 was examined in a panel of 75 continuous human leukemia-lymphoma cell lines originated from different hematopoietic cell types. The presence of the bcl-2 protein, as evidenced by Western blotting, and its mRNA, as determined by Northern blotting, were not restricted to cells with the chromosomal translocation t(14;18)(q32;q21), but were also detected in a large number of cell lines without t(14;18). The amount of the bcl-2 protein and mRNA in the cell lines with t(14;18) was in the same order of magnitude as in other bcl-2 expressing cell lines of the same lineage, but without the translocation. Bcl-2 was found in all types of hematopoietic cell lines which were assigned to the following lineages based on their phenotypical characteristics: pre-B, B, plasma, T, myeloid, monocytic, erythroid-megakaryocytic and Hodgkin's lymphoma derived cell lines. The levels of accumulated mRNA and protein corresponded fairly well in most of the cell lines examined. Our results suggest the notion that bcl-2 expression is widely present in hematopoietic cell lines without restriction to single lineages and, in fact, clearly independent of the chromosomal aberration t(14;18). It is conceivable that bcl-2 expression is a common feature in established hematopoietic cell lines and may contribute to their unlimited growth in vitro.