Granulocyte colony-stimulating factor (G-CSF) has been in clinical use for over a decade. Its main applications are in adjunctive medication to chemotherapy and in mobilizing stem cells for bone marrow transplantation. However, it has additional effects in that it primes neutrophilic granulocytes for improved host defense, and reduces the release of pro-inflammatory cytokines. These effects have prompted trials for numerous other indications. New research into the production and regulation of G-CSF in health and disease may now enable tailored strategies to induce or boost G-CSF formation. Similarly, new forms of application may increase its effectiveness.