Granulocyte colony-stimulating factor (G-CSF) was administered by continuous subcutaneous infusion to 15 patients with non-myeloid malignancies treated by high-dose chemotherapy and autologous bone marrow infusion. G-CSF was given at variable dosage based on neutrophil count. Sustained serum levels of G-CSF were achieved. Neutrophil recovery was accelerated in G-CSF treated patients compared with 18 historical controls and exceeded 0·5 × 109/l at a mean of 11 days after marrow infusion compared with 20 days for controls, a significant difference. This reduction led to significantly fewer days of parenteral antibiotic therapy, 11 versus 18 days in controls, and less isolation in reverse-barrier nursing, 10 versus 18 days.