Liposarcomas are malignant mesenchymatous tumors developed from elements constituting the greasy tissue in various stages of differentiation. It is one of the most frequent mesenchymatous sarcomas. Retro-peritoneum is a privileged site of development in 12 to 15% of cases. During 9 years, from 1994 till 2002, we have colligated and operated 5 cases of retro-peritoneal liposarcomas. Average age was 50 years (extremes 34 to 79 years) with a sex-ratio of 1.5. Diagnosis was late beyond 6 months. Abdominal pain and the appearance of an enormous mass (20 cm) were the revealing signs. No imagery method allowed to evoke the diagnosis. The cyto-puncture realized once, was not able to determine with precision the histological type. Immunohistochimy occupies nowadays an important place to classify a sarcoma. Large surgical resection realized in 5 cases did not allowed the complete ablation of the tumour in 3 cases considering the advanced loco-regional extension, which was at the origin of 3 recurrences. Well differentiated histological type was noted in 3 cases, myxoid type in a case and not differentiated type in a case.