Granulocyte colony-stimulating factor (G-CSF) has been shown to be effective in accelerating neutrophil recovery after BMT. In this single centre study, we have examined the effect of delaying the start of treatment with G-CSF (5 micrograms/kg) until 8 days after BM infusion in a cohort of 17 patients with malignant lymphomas undergoing autologous BMT. In comparison with historical controls, neutrophil recovery to > 0.5 x 10(9)/l was shortened from 22 to 14 days (p < 0.01). Patients receiving G-CSF required iv antibiotics for a median 13 days (control 17, p < 0.05) and were discharged a median 28 days post-ABMT (control 32.5, p = NS). Patients received G-CSF for a median of 10 days only. Although these results require confirmation in a randomised trial they suggest that G-CSF administration could be delayed until 8 days after BMT without compromising efficacy and with an accompanying reduction in treatment costs.