Granulocyte–colony-stimulating factors (G-CSFs) and granulocyte macrophage–colony-stimulating factors (GM-CSF) are substances that bind to hematopoietic stem cells, activating them to proliferate and differentiate into granulocytes and macrophages—the specific cell type of interest. Colony-stimulating factors (CSFs) administered systemically have been evaluated and recommended for patients with cancer for the prevention of infection and febrile neutropenia. CSFs may be used for primary or secondary prophylaxis. A small body of emerging research is investigating the efficacy of different treatment timing and schedules of CSFs on various infection-related outcomes in patients with cancer.