Fludarabine has revealed significant signle agent activity in non-Hodgkin's lymphomas (NHL) in a variety of clinical phase I/II studies. Its efficacy appears most pronounced in low grade NHL and the follicular subtype in particular as well as in Waldenström's macroglobulinaemia. In these disorders, response rates range from 31 to 67% in previously treated patients, and up to 75% in previously untreated patients. Intermediate and high grade NHL subtypes, as well as Hodgkin's disease and lymphomas of the T-cell lineage, appear less responsive. Further improvement may result from combination therapy such as the fludarabine, mitoxantrone, dexamethasone regimen. Prospective controlled clinical trials are needed to compare fludarabine with standard therapies and to define the most appropriate place for this highly promising agent in the treatment of malignant lymphomas.