9024 Background: Angiosarcoma is a heterogeneous group of rare sarcoma types. Its natural history and outcome remains poorly understood. In order to enhance our knowledge and to determine prognostic factors, a retrospective study of angiosarcomas was planned. Methods: Descriptive data of patients with angiosarcomas treated in three institutions between 1980/01/01 and 2004/04/30 were obtained retrospectively. The overall survival and prognostic factors were estimated using the Kaplan-Meier method and Cox’s proportional-hazards models. Hazard ratios (HR) are given with their confidence intervals (CI) at 95%. Results: Median age at the diagnosis was 52 on 161 patients, 35% males and 65% females. Angiosarcomas occurred most frequently in the breast (37.8%), skin (21.2%) and superficial soft tissues (13.2%). Grade 1, 2, and 3 tumors represented 20, 38.9 and 41.1% of documented cases respectively. Tumors were metastatic at the diagnosis in 26,9% of the cases, mostly in lung (25.5%) and 67.3% were multifocal. Surgery was used as first treatment in 80%, chemotherapy and radiotherapy were used in 38.5 and 30% of these patients. With a median follow up of 1.8 years, 56% of patients relapsed, mostly locally and 47.2% died. The median survival was 3.4 years (CI95% 2.4 - 5.8). The overall survival is significantly different according whether patients have or not metastasis at the diagnosis (p=0.0001), their 5-year survival is respectively 23% and 48%, and according to their grade (p=0.03). HR calculated for each angiosarcoma’s localisation (ever/never), after adjusting on age, initial metastatic status and grade, showed that bone (HR 8.7 CI95% 1.6 - 48.3), heart (HR 2.9 CI95% 0.9 - 9.7), and liver (HR 10.8 CI95% 2.7 - 43.4) localisations are bad prognostic factors. Conclusions: Angiosarcomas have a specific pattern of occurrence and relapse, a high risk of relapse and a better prognostic than usually admitted mostly in the metastatic situation. Significant adverse prognostic factors are bone and liver localizations, metastases and histological grade 3. No significant financial relationships to disclose.