The recently proposed World Health Organization classification of neoplastic diseases of the lymphoid tissues is based on the principles of the Revised European-American Classification of Lymphoid Neoplasms introduced in 1994. Use of these classifications implies a new approach to lymphoma diagnosis, especially because of the inclusion of clinical data among which the site of involvement (nodal v extranodal) is very important. Recent technical advances allowing molecular biological investigations on the single cell level helped gain new insights into the cellular origin of B-cell lymphomas. Tumor cells of the majority of B-cell non-Hodgkin's lymphomas (NHL) harbor somatically mutated immunoglobulin variable region genes, and are therefore derived from germinal center B cells or their descendants. The same is true for Hodgkin's disease, which (at least in the majority of cases) is a germinal center derived B-cell lymphoma. Significant news on the molecular pathogenesis of NHL include the prognostically relevant dichotomy of B-CLL, the involvement of translocations affecting 3q27 in 20% to 40% of diffuse large B-cell lymphomas (DLBCL), the prognostical implication of the t(2;5) in anaplastic large cell lymphoma, and detection of the t(11;18) in gastric mucosa-associated lymphoid tissue (MALT)-type lymphoma. A major step forward with regard to gastric MALT-type lymphoma therapy was the discovery of a causal relationship between Helicobacter pylori infection and lymphomagenesis. Cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy remains the golden standard for DLBCL treatment.