The activation of telomerase, which specifically occurs in neoplastic cells to avoid telomere attrition at each cell division, is a necessary event in tumorigenesis. The evidence that telomerase is also present in normal B cells at different levels according to their differentiation and activation state makes the study of telomerase activity in B cell tumors particularly interesting. This review summarizes data concerning telomerase activity in chronic lymphoproliferative disorders of B-cell lineage (B-CLD), making suggestions regarding B-cell development and B-cell tumor histogenesis. The role of telomerase activity as a potential prognostic marker, as well as a target of new antineoplastic strategies is discussed.