The authors reviewed the experience at their institution treating patients with locally advanced breast cancer using multimodality therapy to identify clinical, pathologic, and treatment-related factors affecting outcome. One hundred patients with locally advanced breast cancer were treated with definitive therapy at William Beaumont Hospital. Three patients had stage IIB disease, 45 patients had stage IIIA disease, and 52 patients had IIIB disease. Thirteen patients had inflammatory breast carcinoma. Seventy-four patients (74%) received trimodality therapy consisting of systemic therapy, radiation therapy, and surgery. Systemic therapy was delivered to 90 patients. Eighty-three patients (83%) received adjuvant radiation therapy. Eighty-five patients underwent mastectomy (85%). Multiple clinical, pathologic, and treatment-related factors were analyzed for their impact on outcome. The median follow-up was 47 months. Overall, the 5-year actuarial rates of local control, disease-free survival, overall survival, and cause-specific survival were 81%, 43%, 53%, and 55%, respectively. The 5-year actuarial cause-specific survival rates for patients with inflammatory breast carcinoma, stage IIIA disease, and stage IIIB disease were 25%, 55%, and 53%, respectively. On multivariate analysis, local control was improved with radiation therapy (p = 0.008) and the absence of inflammatory breast carcinoma (p = 0.008). Disease-free survival was improved with the addition of radiation therapy (p = 0.001) and with less than four positive lymph nodes (p = 0.003). Distant metastasis-free survival was improved in patients without inflammatory breast carcinoma (p = 0.0249) and with less than four involved lymph nodes (p = 0.0135). Cause-specific survival and overall survival were adversely affected by the presence of inflammatory breast carcinoma (p = 0.0135 and p = 0.0325, respectively) or four or more involved lymph nodes (p = 0.0082 and p = 0.012, respectively). Radiation therapy appears to be a critical component in the overall treatment of patients with locally advanced breast cancer by improving the rates of local control and disease-free survival. Other adverse factors for survival include four or more positive lymph nodes and inflammatory breast carcinoma.