This study evaluated of the effect of post-transplant recombinant human granulocyte colony-stimulating factor (rhG-CSF) administration on the parameters of peritransplant morbidity. Three sequential and consecutive cohorts of 20 patients each received either post-transplant rhG-CSF at a dose of 5 mug/kg/d i.v. in the morning, starting on d 0, d 5, or no rhG-CSF. Patients who received rhG-CSF starting on d 0 and 5 recovered granulocytes more rapidly than those not receiving rhG-CSF (P < 0.001 for ANC greater than or equal to 0.5 and 1 x 10(9) /l). RhG-CSF administration was not significantly associated with more rapid platelet engraftment. RhG-CSF administration starting on d 0 and 5 was significantly associated with a decreased duration of fever (P = 0.002 and 0.001 respectively), antibiotic administration (P < 0.001 and 0.006 respectively) and shorter hospitalization (P < 0.001 and 0.001 respectively) compared with the reference group. There was no difference between the d 0 and d 5 arms regarding the parameters of peritransplant morbidity. In conclusion, rhG-CSF administration was associated with a faster granulocyte recovery, shorter hospitalization, and shorter period of fever and non-prophylactic antibiotic administration. This study also showed that starting rhG-CSF administration on d 5 may be as effective as d 0 on the clinical outcome and may be an economical approach in routine clinical practice in this cost-conscious era.