The expression of receptors for proliferation and differentiation factors was analyzed by indirect immunofluorescence on 29 Burkitt lymphoma (BL) cell lines previously classified into 3 groups on the basis of their reactivity with 8 monoclonal antibodies (MAbs), including anti-CALLA, BL13 and TU1. BL13 and HB5 antibodies recognize different epitopes of the EBV/CR2 receptors. The determinant recognized by BL13 has been previously shown to be expressed only on cell lines of the first two groups, supposed to derive from the germinal center and to be negative on a third group of lines of putative BM origin and established from sporadic cases of BL. In contrast, and as expected from its reactivity on normal B cells in the BM or in the lymph nodes, HB5 antibody reacts with all BL lines except one. The receptor for transferrin is expressed on the 29 lines. Two new MAbs, Bac-1 and B1H5, could recognize respectively receptors for BCGF1 and BCGF2. Bac-1 reacts with 15 of 17 BL lines belonging to the first two groups and 7 of 12 BL lines of the third group; 14 of 15 EBV + lines express Bac-1. No BL line expresses B1H5. The IL2 receptor is weakly expressed on 5 EBV + cell lines and one EBV (-) line. All delta are BCGF1-positive. The almost constant expression of BCGF1 receptor on EBV + cell lines is the only strict relation between the expression of receptors for growth factors and their characteristics (i.e. EBV association, translocation, ethnic origin and clinical presentation). The maturation stage or the origin of BL cell lines in relation to the expression of growth factor receptors and the functional significance of these receptors will be discussed.