Tumoral lymph nodes (LN) from 7 B-CLL patients were studied with a panel of monoclonal antibodies and in situ immunohistochemical technique. The large majority of LN B-CLL cells carried the phenotype slg+ BA-1+OKIal+ and was admixed with variable numbers of helper/inducer and suppressor/cytotoxic T-cells. In each of the LN studied, regularly distributed, scattered J5+TdT-BA-3- small lumphoid cells were observed, showing no topographical predilection, nor tendency to cluster. J5+ small lymphoid cells may represent pre-B cells which have entered the LN and proliferate and mature in situ, giving rise to a leukemic sIg+OKIal+BA-1+J5- population. This would explain the early generalized LN involvement in B-CLL, and is in agreement with cell-kinetic and compartment in B-CLL LN. Alternatively, J5+ small lymphoid cells may represent a subset of LN B-CLL cells which have acquired the common acute lymphoblastic leukemia antigen during some transformation.