The objective of this study was to describe the cytological and immunophenotypical parameters evocative of B-cell Chronic Lymphocytic Leukaemia (B-CLL) and their ability to participate to the differential diagnosis of other B-chronic lymphoproliferatives disorders with blood dissemination (B-CLD). Two groups of pathology included 92 patients, 79 patients had a B-CLL and the 13 other had a B-CLD (1 Prolymphocytic Leukaemia, 12 non- Hodgkin's Lymphoma in which 4 Splenic Lymphoma with Villous Lymphocytes or SLVL). The lymphoid morphology was studied on blood smear stained with May Gr nwald Giemsa and the immunophenotypical analysis was performed by flow cytometry. The 72 patients with B-CLL were characterized by a predominance of small mature lymphocytes with a Matutes's CLL score 3 (generally CD5+, CD23+, SmIg poor expression). 4 out of B-CLL with cleaved lymphocytes 5 % showed the same immunological characteristics than the typical B-CLL cases. 3 cases of B-CLL with prolymphocytes between 5 and 55 % showed in 2 cases an immunophenotyping compatible with the diagnosis of B-CLD. The presence of shadow cells of Gumprecht was highly evocative of B-CLL. In conclusion, the cytological analysis remains at the root of any diagnosis and can be sufficient in most cases of typical CLL with the presence of shadow cells of Gumprecht on the blood smear. In case of presence of cleaved lymphocytes, the immunophenotyping becomes essential to confirme the diagnosis of B-CLL. In prolymphocytic cases, the differential diagnosis between mixed CLL and B-CLD (especially Mantle Cell Lymphoma and Marginal Zone B-Cell Lymphoma without villous lymphocytes) needs a multidisciplinary approach (clinical, cytogenetical and histological).