Retroperitoneal soft-tissue sarcoma is a rare and unusual entity, comprising about 0.1% of all tumors. Optimal outcome depends on a thorough understanding of its clinical behavior. These tumors tend to be large and have extensive regional involvement by the time they present. Complete surgical extirpation, which may require en-bloc resection of multiple organs, is the treatment of choice for patients who are deemed to be surgical candidates. Chemoradiation has not been proven to extend survival, and treatment toxicities may limit their usefulness. Re-resection of localized recurrent disease may extend survival and therefore should be attempted, when possible. Close follow-up with serial computed tomographic scans is recommended in order to detect early recurrent disease and should continue beyond 10 years.