Fludarabine is an antineoplastic agent which has been studied in patients with a variety of lymphoproliferative malignancies. Clinical evidence from comparative studies in chronic lymphocytic leukaemia (CLL) suggests that fludarabine is at least as effective as CAP (cyclophosphamide, doxorubicin and prednisone) or CHOP (cyclophosphamide, vincristine, doxorubicin and prednisone) in previously treated or chemotherapy-naive patients and significantly more effective than chlorambucil in terms of response rate and duration and survival in chemotherapy-naive patients. Promising results have also been reported with fludarabine-based combination therapy in the treatment of patients with CLL. In addition, sequential therapy with fludarabine and cytarabine has demonstrated good efficacy in the treatment of acute leukaemias, as has fludarabine monotherapy and combination therapy in low grade non-Hodgkin's lymphoma. A favourable cytoreductive response has been reported in patients with lymphoplasmacytoid lymphoma and in a smaller number of patients with cutaneous T cell lymphomas, CLL of T cell origin or prolymphocytic leukaemia. Recent data also support the use of fludarabine, either as a component of a nonmyeloablative conditioning regimen or in the attainment of minimal residual disease, in patients undergoing peripheral blood stem cell or bone marrow transplantation. The tolerability profile of fludarabine is similar to that of CAP, with the most common adverse events being granulocytopenia, thrombocytopenia, anaemia and infection. Alopecia and nausea/vomiting appear to be less frequent with fludarabine therapy than with CAP although the development of immune cytopenias is more frequent with fludarabine. Severe neurotoxicity has been reported with fludarabine but this is mostly confined to the use of high doses. Clinical experience therefore indicates that fludarabine is an effective and generally well-tolerated antineoplastic agent for the second-line treatment of advanced CLL. Recent data from comparative studies also support the earlier use of fludarabine in the treatment of chemotherapy-naive patients with CLL. Furthermore, results of available studies are increasingly highlighting an important future role for fludarabine in the treatment of acute leukaemias and low grade NHL and possibly other lymphoproliferative disorders, particularly when used as a component of combination chemotherapy.