AIMS--To analyse the immunophenotype of a large number of non-endemic Burkitt's lymphomas to determine whether a B cell phenotype is consistently recognisable using formalin fixed, paraffin wax embedded archival material and a standard panel of commercially available antibodies. METHODS--Archival material was obtained from 30 cases of childhood Burkitt's lymphoma registered with the West Midlands Regional Children's Tumour Research Group. These were analysed by a standard avidin biotin complex immunoperoxidase method using antibodies to CD45, CD43, CD30, CD20, CD15, and immunoglobulin heavy and light chains. RESULTS--There was a high incidence of the CD45RB and CD20 immunophenotypes, with a clearly recognisable B cell lineage even in archival material. IgM was identifiable in 13 of the 23 (56.5%) cases tested. Only three of 17 (18%) cases expressed CD30. Positive membrane staining with CD45RO was observed in two (6.7%) cases. CONCLUSIONS--A B cell lineage can be identified in Burkitt's lymphoma in formalin fixed, paraffin wax embedded material, even in archival tissue. There was a low incidence of membrane staining with CD45RO which is a potential source of diagnostic confusion.