High-grade non-Hodgkin's lymphomas (NHL) can potentially be cured with combination chemotherapy, although the optimum schedules still have to be defined. Clinical trials with intensive chemotherapy are predominantly limited by myelosuppression. Here, haematopoetic growth factors open up the possibility of reducing chemotherapy-associated toxicities. In this randomised pilot study, we investigated the effects of a recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) following combined chemotherapy with vincristine, doxorubicin, cyclophosphamide, prednisone and etoposide (VACPE). A total of 35 patients with high-grade NHLs were randomised to receive either rhGM-CSF or placebo during the first two chemotherapy cycles and rhGM-CSF for all following cycles. rhGM-CSF was administered at a dosage of 5 micrograms/kg for 10 days or until neutrophils were > 1/nl following chemotherapy. The analyses revealed a significant reduction of neutropenia and duration of neutropenia in the rhGM-CSF group. Adverse events were rare and generally mild apart from one anaphylactoid reaction. No effects of rhGM-CSF were observed concerning the platelet nadir or duration of thrombocytopenia. The benefit of rhGM-CSF for response induction and survival via rhGM-CSF-supported dose intensification remains to be determined.