There have been significant advances over the last decade in the understanding of cellular, biochemical, and molecular effects of ionizing radiation combined with certain types of cytotoxic drugs and prodrugs, as well as new "targeted" biological agents in human tumor and normal cells. At the same time, new information has evolved regarding specific genetic and epigenetic changes found in certain human cancers, which result in alterations in ionizing radiation damage recognition and damage repair processes. As a result, novel targeting approaches for human tumor radiosensitization is an active area for translational and clinical research in radiation oncology. In this article, we review the current status of existing and new radiosensitizing regimens.