Prolymphocytic leukaemia is an unusual but distinctive variant of chronic lymphocytic leukaemia which generally responds poorly to chemotherapy. Four cases are described to illustrate typical clinical and haematological features and to emphasise the unsatisfactory outcome with combination chemotherapy, radiotherapy and plasma exchange in 3 patients, and to draw attention to the prolonged disease control which followed splenectomy in the fourth. These observations illustrate the relative ease with which the diagnosis can be made and also the difficulties in management, which requires exploration of alternative treatment options.