In this placebo-controlled randomized trial we evaluated the hematological and clinical effects of r-Hu GM-CSF after high-dose chemotherapy (HDC) followed by GM-CSF-mobilized PBPC transplantation. Fifty patients with poor prognosis malignancies were randomized in a double-blind study to receive either GM-CSF or placebo after HDC followed by PBPC rescue. For all patients, PBPCs were recruited using a combination of VP-16 (300 mg/m2 on days 1 and 2), cytoxan (3 g/m2 on days 3 and 4) and GM-CSF (5 micrograms/kg from day 5). No differences were demonstrated between the two groups in median time to neutrophil or platelet recoveries. There was no significant difference between the GM-CSF group and the placebo group in the median duration of post-transplant hospitalization, in the number of days of antibiotic treatment, in the number of infections and in red blood cell or platelet transfusion requirements. There was a significant difference with an advantage for the placebo group in the mean duration of febrile days (P = 0.01). We conclude that the administration of GM-CSF in patients transplanted with GM-CSF-mobilized PBPC is not associated with a clinical benefit in term of tempo of engraftment, numbers of documented infections, transfusion requirements and mucositis grading.