Thirty three B-chronic lymphoproliferative disorder (B-CLD) patients [22 with B-chronic lymphocytic leukemia (B-CLL), 5 with small lymphocytic lymphoma (SLL) and 6 with lymphoplasmacytic lymphoma (LPL)] with anaemia (Ht <32%) of no other cause but their disease, received recombinant human erythropoietin (r-HuEPO). The treatment protocol provided r-HuEPO in a dose of 150 U/kg s.c. thrice weekly for 3 mo. After 1.5 mo of r-HuEPO administration, if response was not satisfactory, r-HuEPO dose escalation was utilised by giving incremental doses of 50 U/kg more than the previous dose up to a maximum dose of 300 U/kg tiw. After maximal response, half of the responding patients discontinued therapy, while the other half received maintenance therapy at a dose of 150 U/kg s.c./w. Oral iron was given throughout the study. Pretreatment EPO levels were determined in all patients. A complete response (CR) was defined when Ht was >38% and a partial response (PR) when there was an increase of the Ht >6% from the initial value was achieved. Sixteen of the 22 B-CLL patients had Rai stage III disease and 6 stage IV, with a median duration of anaemia 27 months (6-38); twelve of them were receiving chlorambucil while the rest were on no treatment. Of the SLL and LPL group, 4 patients had Ann Arbor stage III disease and 7 stage IV with a median duration of anaemia 24 months (5-36); 8 patients were on chlorambucil. Complete response was achieved in 50% of the B-CLL group and 54% of the SLL and LPL group, with an overall response rate of 77% and 81% respectively. All patients on maintenance therapy had a continuous response, while all patients, in whom rHuEPO was discontinued, relapsed. No correlation was found between patients: with low or high pretreatment serum EPO levels; those receiving concomitant therapy or not; those with B-symptoms or not; those with a non-diffuse or diffuse bone marrow infiltration pattern; and with splenomegaly or not. Life quality was significantly improved and no major side effects were encountered. We conclude from our study that r-HuEPO is very effective in correcting disease-related anaemia in B-CLD, resulting in down-staging of Rai stage III patients and that maintenance therapy is necessary. Whether the correction of anaemia improves patients' overall survival, still remains to be seen.