Determinants of prognosis were studied in patients with breast cancer with histologically proven tumor extension to the skin without clinical evidence of distant metastases (i.e., pT4b N0-3 M0). Data were collected retrospectively on 77 consecutive patients diagnosed in one community teaching hospital over the period from 1980 to 1995. The prognostic factor of tumor size showed a 5-year survival rate for patients with a tumor </=3 cm of 81% compared to 45% for patients with tumors larger than 3 cm (p = 0.002). Achievement of complete remission resulted in a 5-year survival rate of 66%, compared to 27% when complete remission was not achieved (p = 0.005). Another important prognostic factor was the development of local-regional recurrence: the 5-year survival rates for patients with and without local-regional recurrence were 39% and 87%, respectively (p < 0.001). Development of local-regional recurrence was also significantly related to tumor size (p = 0.02). Pathologic tumor size and the achievement of complete remission and local-regional control appear to be the most important prognostic factors for survival in patients with pT4b breast cancer without distant metastases. We conclude that the finding of a pT4b breast cancer does not always imply a dismal prognosis, especially for those patients with a tumor </=3 cm. A favorable prognosis can be expected when treatment is effective in achieving complete remission and in preventing the development of local-regional recurrence.