HE t(11;14)(q13;q32) translocation and its molecular T counterpart, bcl-1 rearrangement, were originally reported as recurring cytogenetic and molecular genetic abnormalities in the lymphoproliferative diseases in 1979 and 1984, respectively.'*2 Although sporadic reports of these abnormalities continued to appear in the literature, particularly in the lymphocytic lymphomas and leukemias, no consistent association with any particular lymphoproliferative disease was observed. However, recently several reports3-'' have appeared linking these abnormalities to a distinct histologic subtype of low to intermediate grade lymphoma, which has been called lymphocytic lymphoma of intermediate differentiation (IDL or in the American literature and centrocytic lymphoma (CC)''," in the European literature. The article by Willams et al' in this issue of Blood further strengthens the association of the molecular lesion with this lymphoma subtype. Nonetheless, several questions remain regarding the specificity of the t( 11;14) translocation/bcl-1 rearrangement for IDL/CC and its reported occurrence in other lymphoproliferative diseases. Before we address these questions, it is necessary to review our current understanding of centrocytic lymphoma and IDL.