We carried out a pilot study to evaluate the combined use of recombinant human erythropoietin (rhEpo) and granulocyte colony-stimulating factor (G-CSF) for accelerating marrow engraftment in children given allogeneic bone marrow transplantation (BMT). Fifteen consecutive children were enrolled in this study; 13 completed it and were evaluable. Using analysis of variance, laboratory and clinical data referring to these children were compared with those of 15 patients previously treated with rhEpo alone and with those of 16 historical controls. Erythroid repopulation, evaluated sequentially through serum transferrin receptor and reticulocyte count, was similarly accelerated in children receiving rhEpo alone and in those receiving combined treatment. These latter, however, showed a further reduction in the total number of red blood cell units required to reach transfusion independence (1.1 +/- 0.7 in the study population vs 2.7 +/- 1.2 in rhEpo group vs 4.2 +/- 2.3 in historical controls; values are mean +/- 1 SD; p < 0.001). Neutrophil engraftment, i.e. time for neutrophils to reach 0.5 x 10(9)/l, was 11 +/- 3 days in children receiving combined treatment, significantly shorter than that of the control groups (16 +/- 3 and 18 +/- 5, respectively; p < 0.001). Acceleration of neutrophil recovery translated into fewer infections: days of fever were significantly reduced in the study population (4 +/- 2 vs 11 +/- 8 vs 15 +/- 6, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)