Despite wide efforts for early detection of breast cancer using screening mammography, locally advanced breast carcinomas account for a remarkable proportion of all breast carcinomas, particularly in developing countries. Locally advanced breast cancer may have widely different clinical and biological features. Radiotherapy plays an important role in the management of locally advanced breast cancer. Postmastectomy radiotherapy has been shown to significantly reduce the risk of loco-regional failure and to improve disease free survival as well as overall survival in high-risk women with breast cancer. This review article summarizes the data from randomized trials revealing a significant benefit from postmastectomy radiation therapy in patients with locally advanced disease.