The discovery of the haematopoietic growth factor granulocyte colony-stimulating factor (G-CSF) has reduced infection-related morbidity in cancer patients by alleviating post-chemotherapy neutropenia. Two formulations of recombinant human (rh) G-CSF, one glycosylated and one non-glycosylated, are available. The glycosylated form, lenograstim, possesses at least 25% greater bioactivity in vitro. Some comparative studies into the preparation's potential to mobilise haematopoietic stem cells suggest a similar advantage. In the light of the great clinical importance of G-CSF, we have performed the first prospective, randomised, crossover study on children with chemotherapy-induced neutropenia. G-CSF (250 microg/m(2)) was started 1 day after the chemotherapy block, and was administered until a WBC >1500/microl was achieved on 3 successive days. Thirty-three G-CSF cycles from 11 patients (16 lenograstim, 17 filgrastim) were studied. They were investigated for duration of very severe (WBC <500/microl, 9 vs 9.5 days, lenograstim vs filgrastim, median) and severe leukopenia (WBC <1000/microl, 11 vs 11 days), infections (CRP >5 mg/dl, 5 vs 5.5 days), infection-related hospital stay (11 vs 9 days) and antibiotic treatment (9 vs 9 days). Statistical evaluation by paired analysis could not detect any difference between treatment groups; the median difference for all end-points was zero. In summary, at least at 250 microg/m(2), in terms of their clinical effect on neutropenia, the two G-CSF preparations appear to have identical activity.