We report a case of angiosarcoma of the large bowel in a 66 year old man with histochemical, immuno histochemical and ultra structural study. The patient subsequently completed non surgical staging, showing no extension of the tumor. No etiologic factor was found. Despite complete surgical exeresis, the clinical course is rapidly fatal with occurrence of numerous metastases. Primary angiosarcoma of the gastro intestinal tract are very uncommon. According to the degree of differentiation the diagnosis of large bowel's primary angiosarcoma can be difficult with others large bowel sarcoma, a benign blood vessel tumor or an undifferentiated carcinoma. The immuno histochemical and ultra structural study are useful to perform the diagnosis of angiosarcoma.