Polymerase chain reaction (PCR) and immunohistochemical staining methods were used to detect the bcl-2/IgH fusion gene [t(14:18)] and the overexpression of bcl-2 protein in 28 cases of follicular lymphomas and 18 cases of reactive follicular hyperplasia. The results showed that the bcl-2/IgH fusion gene was present in 57% of follicular lymphomas and that this translocation was also present in 33% of the reactive follicular hyperplasia cases. The over expression of bcl-2 protein was found in 78% of follicular lymphomas, but none in follicular hyperplasia, therefore bcl-2 protein staining may be a useful immunohistochemical method to differentiate follicular lymphoma and follicular hyperplasia.