The toxicities and possible utility of the combination of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) and recombinant human erythropoietin (rHuEPO) given after autologous BMT were evaluated in this pilot trial. Eighteen patients received the combination and were compared with six concurrent control and 65 historical control patients treated with rhGM-CSF alone. Patients treated with the combination tended to have more rapid recovery to an absolute neutrophil count of 500 x 10(6)/l (median = 12.5 vs 18 days for concurrent and 19 days for historical control patients). There was no apparent impact on red cell transfusion requirements, platelet recovery or duration of hospitalization. Patients treated in the current study with rhGM-CSF plus either rHuEPO or with placebo had a higher incidence of rash than seen in our historical experience using rhGM-CSF. This difference may reflect changes in the source of rhGM-CSF or in the infusion schedule. Erythropoietin can be combined safely with rhGM-CSF after autologous transplantation. Larger controlled trials will be necessary to detect possible therapeutic effects.