The importance of dose intensity has been strongly emphasized in high-risk breast cancer. Overexpression of erb B2 is clearly correlated with an overall poor prognosis which could be limited in patients receiving intensive chemotherapy with alkylating agents and autologous stem cell transplants (SST). Thirty-five patients with high-risk non-metastatic breast cancer (>4 involved lymph nodes), treated with high-dose chemotherapy (HDC) followed by SST were analyzed. All were previously treated by four cycles of standard-dose anthracycline or anthracene dione. Nine had erb B2 overexpression. Minimum follow-up duration was 41 months (median 68 months). At 5 years, the actuarial relapse-free survival is 57.4% and actuarial overall survival 67.4%. Patients with overexpression of erb B2 had significantly lower disease-free survivals (P: 0.021) and overall survivals (P: 0.001). On multivariate analysis, erb B2 overexpression appeared to be the single independent poor prognosis factor for relapse (RR 3.25, range 1.12 to 9.45) and overall (RR 5.28, range 1.74 to 16.03) survival. These results suggest that poor prognosis of erb B2 overexpression is unchanged after HDC with alkylating agents but a possible benefit may exist in these patients with the additional monoclonal antibody, herceptin.