The various aspects of this comparatively rare neoplasia are discussed on the basis of two cases of retroperitoneal liposarcoma and an analysis of the literature. Consideration are expressed on the clinical symptoms, the pathological anatomy, its marked tendency to evolve with repeated local relapses and the need to properly localise the mass and the feeding peduncles prior to the operation, so that radical exercise can be performed, since this leads to a more favourable long-term prognosis. The utility of radiotherapy, which leads to a lengthened period of freedom from the disease and to an increased survival time, is also stressed.