Myeloid growth factors have significantly improved the quality of life and reduced the morbidity of patients experiencing chemotherapy-induced neutropenia or undergoing bone marrow transplantation. However, in only a few instances have they directly contributed to improved response rates, better disease-free survival, or decreased mortality. With their increased use, concern has risen about their cost-effectiveness and appropriateness. To justify the use of myeloid growth factors and maximize patient benefit while minimizing the cost to health care systems and society, the development of guidelines for the clinical use of these expensive drugs is of great importance. In recent years both a European and an American expert panel have tried to establish consensus guidelines based on published evidence. A remarkable agreement can be found between results of both working parties. Clear recommendations for an optimal and more rational use of myeloid growth factors in clinical practice on both sides of the ocean have been delineated.