Splenic lymphoma with circulating villous lymphocytes is a rare B-lymphoproliferative disorder of the elderly which has been only recently defined. Clinical features are spleen enlargement of various degree without lymphadenopathy and an indolent course, with a long survival, in most cases. Absolute lymphocytosis is present; atypical circulating lymphocytes show a medium or large size, a small prominent nucleolus and a few short and thin cytoplasmic protrusions and projections (villi), which are distributed at one or both poles of cell surface. Reaction for tartrate-resistant acid phosphatase is almost always negative. Immunological markers are as follows: CD 19+, CD 20+, CD 22+, CD 11c+/-, CD 5-, CD 23-, CD 25-, HLA DR+, SmIg+. Differential diagnosis with other chronic lymphoproliferative disorders, particularly chronic lymphocytic leukemia, hairy cell leukemia, prolymphocytic leukemia, follicular and mantle-cell lymphoma in leukemic phase, is based on clinical and immunocytomorphologic criteria. Bone marrow biopsy shows involvement of different degree and pattern; splenic involvement mostly occurs in the white pulp; hepatic nodules in portal areas may be present. Cytogenetic alterations are often present but not specific, such as increased serum LDH and monoclonal gammopathy. No therapy should be made in asymptomatic patients. In case of systemic symptoms, symptomatic splenomegaly or cytopenias, treatment may consist on splenectomy, splenic irradiation or alkylating agents. A case of splenic lymphoma with circulating villous lymphocytes is reported; differential diagnosis, particularly with other B lymphoproliferative disorders, is discussed.