Several studies have shown conflicting results with the use of intensive consolidation chemotherapy for breast cancer. The aim of the present study was to investigate the efficacy, feasibility and toxicity of high-dose chemotherapy with stem cell support in patients with high-risk stage II breast cancer. From February 1994 to November 1998, 132 consecutive patients with multinode positive breast cancer were entered to the study. In total, 86 patients had >or=10 positive axillary lymph nodes, and 46 had 4-9 positive axillary lymph nodes with at least two additional predetermined risk factors at diagnosis. All patients were offered adjuvant chemotherapy (doxorubicin, 75 mg/m(2) x 4) followed by high-dose chemotherapy (cyclophosphamide 6000 mg/m(2), carboplatin 800 mg/m(2) and thio-tepa 500 mg/m(2)) and autologous stem cell support with growth factor. In all, 131 patients also received local radiation therapy and tamoxifen based on receptor status. After a median follow-up of 51 months (range 27-87), the disease-free and overall survival rates were 72 and 81%, respectively. There was no difference in the outcome for high-risk patients with > or < than 10 positive axillary lymph nodes. On Cox regression analysis only progesterone receptor status was predictive of disease-free, but not overall survival. There were no treatment-related deaths; grades III-IV toxicity was relatively low. This combined approach of doxorubicin followed by high-dose chemotherapy and stem-cell support, followed by locoregional radiotherapy, was safe and seems to be effective in patients with multinode positive stage II breast cancer. In previous trials of adjuvant high-dose therapy in this patient population, treatment-related morbidity and mortality markedly influenced the outcome. For this high-risk patient population, further testing of intensive chemotherapy regimens with a lower toxicity profile is warranted.