The study was designed to determine the toxicity, feasibility, and effectiveness of high-dose cyclophosphamide (6 g/m2), thiotepa (500 mg/m2) and carboplatin (800 mg/m2 (CTCb) with hematopoietic rescue as consolidation after standard-dose adjuvant chemotherapy treatment of primary high-risk breast cancer. From October 1991 to September 1994, 40 patients with stage II or III breast cancer involving 10 or more nodes were treated with CTCb after six cycles of adjuvant therapy with an anthracycline-containing regimen. Bone marrow (BM) was used as the source hematopoietic stem cell in the first 23 patients and G-CSF-mobilized peripheral blood progenitor cells (PBPC) in the other 17. No therapy-related deaths occurred, but three life-threatening Complications were recorded which resolved: bilateral pulmonary hemorrhage, veno-occlusive disease of the liver and pulmonary thromboembolism. PBPC result in faster hemopoietic reconstitution with significantly lower transfusion requirements. With a median follow-up of 35 months (23-59) actuarial event-free survival for the study patients at 3 years is 72% (CI 95%: 66-81%). Even in patients over 50-60 years, CTCb is a relatively well tolerated regimen which appears, after a median follow-up of nearly 3 years, to decrease relapse frequency as compared with historical series, although a definite role of HDT in the treatment of high-risk primary breast cancer needs confirmation in prospective randomized trials.