Using reverse transcription and the polymerase chain reaction (RT-PCR), we determined the level of expression of BCL-2/IgH in 18 follicular center cell lymphomas containing a t(14;18) translocation involving the major breakpoint region and five non-neoplastic lymph nodes. BCL-2/IgH transcripts were demonstrated in 16 follicular center cell lymphoma cases (five high, 11 low) and were not present in any of the five non-neoplastic lymph nodes. In the two follicular lymphoma cases in which BCL-2/IgH transcripts could not be detected by RT-PCR, PCR amplification of genomic DNA indicated this was not due to primer selection. In addition, non-expression was confirmed at the protein level by immunoperoxidase studies. We therefore conclude that these represent true negative cases. This is the first time primary follicular lymphoma cases have been quantitatively studied at the RNA level for expression of BCL-2. We conclude that RT-PCR is a sensitive method for determining levels of expression of this oncogene and may be useful in studying the involvement of BCL-2 in follicular lymphoma.