Cells of 7 EBV‐B‐LCL, 10 Burkitt lines and 13 EBV‐B‐LCL/Burkitt line hybrids have been phenotyped for antigens of the major B cell clusters and for some other antigens. High levels of CD23 and CD39 and low levels of CD38 (T10) were characteristic of EBV‐B‐LCL; the converse was true for Burkitt lines. In hybrids the EBV‐LCL phenotype was dominant. The phenotype of Burkitt‐line cells correlated strongly with that of germinal centre B cells in tonsil sections, but differed markedly from that of marginal zone B cells or follicular mantle cells. The results are discussed in relation to the origin of Burkitt tumours of “sporadic” and “endemic” type, in particular to histopathological evidence that Burkitt lymphomas develop in germinal centres. Recent studies on the location of the breakpoints of Burkitt chromosomal translocations are also considered to be compatible with this concept, even though different regions of the immunoglobulin heavy chain locus are involved in the two types of BL.