During the last century management of breast cancer became increasingly less aggressive for small tumors. Randomized trials demonstrated similar overall survival between mastectomy and breast-conservative surgery (BCS) followed by adjuvant radiation therapy (RT). BCS plus adjuvant RT +/- systemic therapy has become the standard of care for women with early breast cancer. Advances in modern RT technology allowed significant increase in high precision of target definition. Intensity modulated radiation therapy (IMRT) and gating, under investigation in miscellaneous cancers, are also in development for breast-cancer patients. These techniques decrease radiation toxicities and could be useful in the setting of concurrent use of RT and new systemic therapies such as trastuzumab. Another advance in RT is the development of accelerated partial breast irradiation (APBI) as a new concept in the adjuvant setting for early-stage breast cancer. Intraoperative RT (IORT), immediate postoperative RT (interstitial brachytherapy or Mammosite device implantation) and delayed postoperative RT (external beam of photons or protons with 3D conformation) are under investigation. In this review, the role of modern whole breast irradiation is discussed, the rational of partial breast irradiation is argued and the different techniques are detailed.