LWBL is characterized by persistent and stable lymphocytosis, seen in but not exclusively female patients, with binucleated lymphocytes evident on peripheral blood smears. There is a polyclonal increase of serum IgM and in all cases immunophenotyping revealed a polyclonal expansion of B-lymphocytes. Whether this syndrome represents a premalignant disease process or a true polyclonal lymphocytosis remains unsettled. The occasional reports of clonal Ig rearrangements in this disorder suggest that in a minority of cases the polyclonal expansion may be followed by the emergence of one predominant clone. The demonstration of a clinically, benign, clonal lymphoid population is well recognised in several T cell disorders such as in the syndrome of large granular lymphocytes expansion. The benign clinical course and the lack of biological evolution in the majority of cases suggest that the importance of recognition of this disorder lies in avoiding aggressive therapy in these cases. A careful follow-up of these patients is mandatory and prospective immunological and genetic studies performed at different stages of the disease may well clarify this issue, particularly since most patients were HLA-DR7 positive.