This report describes the occurrence of splenic lymphoma with villous lymphocytes (SLVL) in a 56 year old white female with a family history of chronic lymphocytic leukaemia. Other unusual features included a marked lymphocytosis with counts up to 224 x 10(9)/l and marked clumping of lymphocytes in EDTA anticoagulated blood. The neoplastic cells were CD19+, CD20+, CD22+, CD22+, IgM+, lambda+, kappa-, CD5-, and CD10-. The spleen had nodular infiltrates of B lymphocytes in the region of the white pulp with minimal red pulp involvement. Electron microscopy of peripheral blood lymphocytes revealed cells with polar cytoplasmic processes. This report underlines the need for detailed analysis, including morphology and immunophenotyping, for each patient with a small B cell lymphoproliferative disorder.