The high incidence of breast cancer in young women, and the unfavorable prognosis for those who present with a high number of lymph nodes involved with cancer, has encouraged the development and evaluation of new treatment strategies. The use of dose intensification is supported by laboratory and clinical models. In this review article, the use of dose intensification supported by hemopoietic growth factors, and also by hemopoietic stem cells, is discussed. The results of published studies of high-dose chemotherapy in Stage II, III, and IV breast cancer are discussed and summarized, including those randomized comparisons with more conventional therapy. Improvements in supportive care continue to reduce the risks from neutropenia and thrombocytopenia, and these and other toxicities are likely to decrease as side-effects are anticipated and experience increases.