Effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF, filgrastim) on hematopoietic recovery and clinical outcome in patients undergoing allogeneic bone marrow transplantation (BMT) from volunteer unrelated donors (VUD) were analyzed retrospectively. Additionally, the influence of baseline patient and transplant characteristics on hematopoietic recovery was evaluated. From January 1994 to March 1996, 47 consecutive adult patients received VUD-BMT. GVHD prophylaxis was cyclosporin A/short course methotrexate/prednisolone, and in four patients additional ATG. Post-transplantation, cohorts of patients received rhG-CSF (5 microg/kg/day) (n = 22) or no rhG-CSF (n = 25) in a non-randomized manner. The patient groups with and without rhG-CSF were rather comparable with respect to baseline patient and transplant characteristics. Median time to neutrophil counts (ANC) >500/microl was 14 days with rhG-CSF vs 16 days without rhG-CSF (P = 0.048), to ANC >1000/microl was 15 vs 18 days (P = 0.084). Neutrophil recovery was accelerated in patients receiving more than the median MNC dose of 2.54 x 10(8)/kg with a median time to ANC >1000/microl of 13 days vs 19 days (P = 0.017). RhG-CSF did not influence platelet recovery and incidence of infectious complications. Incidence of acute GVHD II-IV was 50% with rhG-CSF and 28% without rhG-CSF (P = 0.144), but death before acute GVHD II-IV occurred in 9% of patients with and 20% of patients without rhG-CSF. The median follow-up time was 38 and 36 months in patients with and without rhG-CSF, respectively. Survival at 2 years post-transplant was 39% (95% confidence interval (18%, 60%)) in patients with rhG-CSF and 24% (95% confidence interval (7%, 41%)) in patients without rhG-CSF. Administration of rhG-CSF after VUD-BMT may lead to more rapid neutrophil recovery, but did not influence the incidence of infectious complications. Patients receiving rhG-CSF showed a slightly higher incidence of acute GVHD II-IV. Higher numbers of MNC in the marrow graft accelerated hematopoietic engraftment.