Despite adjuvant chemotherapy the prognosis of patients with breast cancer and a high number of involved axillary lymph nodes is very poor. The aim of the present study was to evaluate the efficacy of high-dose chemotherapy with autologous bone marrow support in patients with seven or more involved axillary lymph nodes. Nineteen patients underwent four courses of standard adjuvant chemotherapy, followed by high-dose busulphan/cyclophosphamide chemotherapy with autologous bone marrow support. The median age was 41.4 years and the median number of involved lymph nodes 11. Mucositis WHO grade > or = 3 was observed in 15 patients and 18 patients suffered febrile neutropenia. Transplant-related mortality was encountered in two patients, due to hepatic veno-occlusive disease and sepsis complicated by multi-organ failure, respectively. After a median follow-up period of 1490 days (range 582-2024 days) from diagnosis, nine patients have relapsed and the overall event-free survival (EFS) is 42% (95% CI 19-65%). The median EFS is 487 days. High-dose treatment with BuCy2 in high-risk breast cancer patients is a toxic regimen and does not seem to improve disease-free survival.