An international panel of radiation oncologists who specialize in sarcoma reached consensus guidelines for preoperative radiation therapy (RT) for retroperitoneal sarcoma (RPS). Many of the recommendations are based on expert opinion because of the absence of higher level evidence and thus, are best regarded as preliminary. At the time of publication, the guideline developers were awaiting data from the European Organization for Research and Treatment of Cancer (EORTC) study of pre- operative radiotherapy plus surgery versus surgery alone for patients with RPS. Further data are also anticipated pertaining to normal tissue dose constraints, particularly for bowel tolerance. Nonetheless, the guidelines can be used to establish treatment uniformity to aid future assessments of efficacy and toxicity.