Partial breast radiotherapy (PBRT) has recently gained an optional place as local adjuvant treatment after breast-conserving surgery (BCS) for selected early-stage breast cancer. With high-dose-rate (HDR) interstitial multicatheter brachytherapy (BT) performed under strict quality assurance criteria, there is level B evidence derived from one single randomized study with follow-up longer than 5 years and level C from several mature prospective non-randomized studies. For intra-lumpectomy cavity Mammosite HDR-BT and for external beam RT, as well as 3-dimensional (3D)-conformal or intra-operative therapy by electrons or photons, there is only level D evidence with no mature enough prospective data. Large phase III trials are ongoing for each PBRT technique, but their results might offer a level A evidence no earlier than 5 years.