Soft tissue sarcomas are rare tumours with infrequent identified aetiological factors. Several genetic syndromes as well as previous radiation therapy and/or chronic lymphoedema have been suspected to predispose to some soft tissue sarcomas. Between January 1997 and September 2005, we carried out a prospective descriptive study to estimate the frequency of some particular etiological factors among 658 patients with soft tissue sarcomas. Sarcomas associated with a clinically identified genetic disease represent 2.8% out of all cases (95%CI: 1.5-3.8%). Most of these cases (14/19) are related to Recklinghausen neurofibromatosis. Radiation-induced sarcomas represent 3.3% out of all cases (95%CI: 1.7-5.1%). Most of these cases (9/22) are related to prior breast cancer treatment. We had observed only 1 case of Stewart-Treves syndrome. Liposarcoma, the most frequent histological subtype observed, is not associated with any particular aetiological entity. Finally, most of the adult soft tissue sarcomas are not related to any classical clinically identified genetic disease or previous radiation therapy and/or chronic lymphoedema risk factors. Frequency of underlying genetic syndrome which may predispose to soft tissue sarcomas could be higher than previously reported.