Myelosuppression continues to be a major dose-limiting toxicity for most chemotherapy regimens. While the development of growth factors has changed the approach to myelosuppression, costs remain high and can be measured both in terms of quality of life (QOL) and economic outcomes. Growing data suggest that there may also be effects on response and survival in some tumors. This review will highlight the incidence, effect, and treatment/prevention of myelosuppression and briefly discuss the questions that remain.