Prolymphocytic leukaemias of B and T cell subtype are rare diseases. Despite recent advances in immunophenotyping and molecular cytogenetics, leading to a better understanding of the underlying cell biology of the prolymphocytic leukaemias, prognosis for these patients remains poor. Purine analogues and monoclonal antibodies have shown efficacy in B-cell prolymphocytic leukaemia although further studies are warranted. Monoclonal antibody therapy with alemtuzumab has significantly improved outcome in T-cell prolymphocytic leukaemia (T-PLL) but responses are still transient and further disease progression is inevitable. While allogeneic stem cell transplant is an attractive option, due to the older age group of T-PLL patients the morbidity and mortality associated with the procedure is significant.