The bcl-2 (B-cell leukaemia/lymphoma 2) proto-oncogene is associated with the 14;18 translocation in follicular lymphoma juxtaposing bcl-2 with the immunoglobulin heavy chain region. bcl-2 has been cloned and sequenced and a monoclonal antibody to amino acids 41 to 54 of the bcl-2 protein has been raised. The expression of bcl-2 in follicular lymphoma has been demonstrated by immunohistological staining and also in normal lymphocytes. The presence of the bcl-2 onco-protein has been demonstrated by immunofluorescence using conventional and confocal microscopy in normal and malignant plasma cells from myeloma patients and myeloma cell lines. Plasma cells from 8/8 normal donors were positive, although the proportion of positive cells and the intensity of staining varied. Eight of 10 patients with myeloma or plasma cell leukaemia had positive plasma cells, and 6/11 plasma cell lines and one lymphoma cell line also expressed the onco-protein. bcl-2 expression is a feature of normal plasma cells and data from the cell lines confirm that expression is not dependent on the presence of the 14;18 translocation.