Accelerated partial breast irradiation (APBI) is being rapidly introduced into the clinical management of early breast cancer. APBI, in fact, encompasses a number of different techniques and approaches that include brachytherapy, intraoperative, and external beam techniques. This text is a concise handbook designed to assist the clinician in the implementation of APBI. It includes a review of the principles that underlie APBI, a practical and detailed description of each technique for APBI, a review of current clinical results of APBI, and a review of the incidence and management of treatment related complications.