A patient with a nodular and diffuse small-cleaved follicular center-cell lymphoma that exhibited definite plasmacytic differentiation, a related monoclonal gammopathy, and circulating population of small lymphocytes is presented. Aside from showing that the presence of numerous plasma cells is not a reliable criterion for the diagnosis of a reactive follicular proliferation, the case is an example of a lymphoma without a block in maturation. The "neoplastic" B-cells show development to follicular center cells and beyond, to functioning plasma cells, and probably also to recirculating "memory" cells. It also suggests that plasmacytoid lymphocytic lymphomas (Lukes-Collins classification) might represent a heterogeneous group of lymphoid neoplasms with some closely related to follicular center-cell lymphomas and others more closely related to small lymphocytic lymphoma/B-cell chronic lymphocytic leukemia.