Seven tonsillar B cell sub-sets have been isolated according to cell surface molecular markers. The molecular characteristics of their phenotype, cell cycle, survival, somatic mutations and isotype switch status permit their inter-relationships to be followed up until the plasma cell stage. Different lymphoma types correlate with all except one of the stages and only two out of nine non-Hodgkin's B cell lymphomas cannot be presently associated to a normal peripheral B cell sub-set. The assignment of lymphomas to their normal human B cell counterparts will facilitate the identification of the causative event(s) responsible for the malignant transformation.