The American Society of Clinical Oncology (ASCO) recently updated its guidelines for the use of hematopoietic colony-stimulating factors (CSFs). The 2005 update committee unanimously agreed that the reduction in febrile neutropenia (FN) was an important clinical outcome that justified the use of CSFs, regardless of impact on other factors, when the risk of FN was approximately 20% and no other equally effective regimen that did not require CSFs was available. The first guidelines were published in 1994, and they were updated in 1996, 1997, 2000, and, most recently, 2005.