In 29 chemotherapy-naive patients with stage II-III breast cancer, peripheral blood stem cells (PBSCs) were mobilised following fluorouracil 500 mg m-2, epirubicin 90-120 mg m-2 and cyclophosphamide 500 mg m-2 (FEC) and granulocyte colony-stimulating factor (G-CSF; Filgrastim) 300 microgram s.c. daily. This evidence concerns the gene CSF3 and breast cancer.