Retroperitoneal soft-tissue sarcoma is an uncommon cancer of mesodermal origin, which is difficult to treat owing to its location and proximity to vital structures. Complete gross resection, often involvingen blocresection, is the standard of care as it represents the only treatment that improves overall survival. Unlike extremity sarcoma, retroperitoneal soft-tissue sarcoma tumor mortality is from local recurrence. Radiation therapy is the only adjuvant treatment that has improved local control in several institutional series. However, there remains no definitive prospective, randomized trial that establishes the role of adjuvant radiation versus no radiation. Owing to significant radiation morbidity with adjacent organs, especially the small bowel, there exists no consensus on radiation timing, delivery method or dosing. Recent and current protocols use preoperative external-beam radiation with or without a method of focal boost dosing. Methods of boost dosing include brachytherapy, intraoperative radiation therapy and intensity-modulated radiation therapy. Further studies are needed to definitively include radiation therapy in the standard treatment of retroperitoneal soft-tissue sarcoma and to find the optimal balance between acceptable radiation toxicity and effective local control in treatment protocols.