An inconsistent association exists between EBV-LMP-1 and bcl-2 protein expression in Reed-Sternberg cells seen in Hodgkin's disease. In fact, many studies have concluded that there is no correlation between EBV-LMP and bcl-2 expression in Hodgkin's disease. We undertook an analysis of post-transplant lymphoproliferative disorders to explore the relationship between EBV-LMP and bcl-2 in Reed-Sternberg-like cells found in this condition, given the strong association between this disorder and EBV. Reed-Sternberg-like cells were found histologically in 11 of 28 cases of renal, heart and heart-lung post-transplant lymphoproliferative disorders. Formalin-fixed, paraffinembedded sections were stained with monoclonal antibodies to EBV-LMP-1 and bcl-2 proteins. Reed-Sternberg-like cells in all 11 cases co-expressed EBV-LMP and bcl-2. A similar relationship was noted with large, mononuclear cells and occasional small lymphoid cells. The staining pattern seen with both antibodies was of similar intensity and both displayed cytoplasmic Golgi accentuation. In the setting of post-transplant lymphoproliferative disorders. Reed-Sternberg-like cells exhibit strong co-expression of EBV-LMP-1 and bcl-2 proteins, supporting a positive correlation between them. This is in contrast to the findings in Hodgkin's disease. The reason for this discrepancy may be due to the iatrogenic immunosuppression and resultant severe EBV infection, together with other cellular events.