Breast-conservation therapy (BCT), consisting of lumpectomy followed by whole-breast irradiation (WBI), is the standard of care for women with early-stage breast cancer. However, many women who are candidates for BCT either choose mastectomy or lumpectomy alone for myriad reasons. Accelerated partial-breast irradiation (APBI) is a collection of radiotherapy techniques that deliver higher daily doses of radiation to the surgical cavity with margin over a shorter time than WBI, reducing total treatment time from 6-6.5 weeks to 1-2 weeks. Advocates of APBI state that early results of this approach demonstrate excellent local control, minimal acute toxicity, and are associated with more convenience for the patient. Phase III randomized clinical trials are currently underway to assess local control, acute and chronic toxicities, and quality of life associated with APBI compared to WBI. In this review, we hope to clarify the rationale behind APBI and discuss in depth data concerning various partial-breast irradiation techniques that are being used throughout the United States and around the world.