A brief historical review and a unifying classification of the non-Hodgkin's lymphomas are presented. The principles underlying this classification are that 1) ncoplastic cells are named after normal cells they resemble most; 2) the germinal center is a reaction center where small lymphocytes undergo blastic transformation as well as the birthplace of small lymphocytes; and 3) lymphoid cells can be subdivided by size and cytologic characteristics into small, intermediate, and large types. This classification can be expanded by additional qualifying terms. Whether such expansions are justified in terms of reproducibility and clinical significance remains to be proven.