In the first part of the last century, radiation therapy was considered an empirical, clinical discipline. This situation has changed considerably during the past 40 years. This change from an empirical and clinical discipline to a precise clinical science has been accompanied by innovations in physics and technology. Within the last 2 decades, a number of new challenging radiation therapy modalities has come into the practice of radiation oncology. This includes:Particle beam therapy, Intraoperative radiotherapy, 3DCRT, Stereotactic radiotherapy and radiosurgery, IMRT, IGRT and Radioimmunoglobulins.