High-dose chemotherapy using transplantation of hemopoietic precursor cells offers much advantage for treatment of prognostically unfavorable cancers of the breast. Both experimental and clinical evidence points to a potential of raising antitumor effect by increased dosage of chemical drugs. Clinical studies using high-dose chemotherapy for treating patients with stage II-III tumors or with greater than or equal to 10 positive axillary lymph nodes, and locally-advanced and disseminated tumor established a relative rise in overall and recurrence-free survival, as compared with standard treatment. Hazardous cytopenia and related complications can be significantly reduced when hemopoietic precursor cells are transplanted from peripheral blood.