Bcl-6 is a proto-oncogene that encodes a Kruppel-type zinc-finger protein of 95 kD and shares homology with other transcription factors. Bcl-6 is mainly expressed in normal germinal centre B cells and related lymphomas. It has been shown that Bcl-6 is involved in chromosome rearrangements at 3q27 in non-Hodgkin=s lymphomas and Bcl-6 rearrangements have been detected in 33 to 45 per cent of diffuse large B cell lymphomas. Immunohistochemistry has shown the Bcl-6 gene product to be detected in follicular lymphomas, diffuse large B cell lymphomas, Burkitt's lymphomas and in nodular, lymphocyte predominant Hodgkin's disease.