Accelerated partial breast irradiation as the sole radiation modality following lumpectomy has shown promising results for select breast cancer patients. Brachytherapy, as the method of delivery, required a large volume implant with catheters placed in and around the seroma cavity and was technically challenging. Image guided brachytherapy implants followed by image assisted 3D dosimetry planning has made the process more accurate. Due to its enormous demand of skill, time and physics resources, physician acceptance remained low. Development of Mammosite balloon has simplified both the implant procedure and the dosimetry planning. Recently, the development of an external beam technique that would mimic brachytherapy techniques has been developed. Since most radiation therapy clinics have a CT scanner, physics planning software and linear accelerator necessary to perform 3D conformal accelerated radiation, external beam modality of delivering radiation has become the obvious choice. This chapter reviews these three techniques and the rationale and dosimetric outcomes are highlighted in this review.