Diffuse large B-cell lymphomas (DLBCL) represent the most common type of adult non-Hodgkin's lymphomas in Western countries and are characterized by heterogeneous clinical, histological, immunophenotypic and genetic features. Recent investigations using cDNA and oligonucleotide microarrays have identified molecularly distinct groups of DLBCL with respect to the B-cell differentiation gene expression profile: the germinal center (GC) B-cell-like DLBCL, the activated B-cell-like DLBCL and the type 3 DLBCL. The GC B-cell-like DLBCL were characterized by the expression of genes of the normal GC B-cells, the activated B-cell-like DLBCL were characterized by the expression of genes that are normally induced luring in vitro activation of peripheral blood B-cells, while the type 3 DLBCL did not express either set of genes at a high level. Patients with GC B-cell-like DLBCL had more favorable clinical outcome than those with activated B-cell-like or type 3 DLBCL. Immunohistochemical studies have shown that the bc16/CD10/MUM1/CD138 B-cell differentiation immunophenotypes are prognostically relevant and may predict the cDNA classification in a sizable fraction of DLBCL. In the last few years, there has been accumulating molecular and immunohistochemical evidence indicating links between B-cell differentiation gene expression profiles and expression of apoptosis and cell cycle-associated genes in DLBCL. The present review summarizes data with respect to the relationships between B-cell differentiation, apoptosis and proliferation in DLBCL.