Since the advent of endothelial cell specific antibodies, immunocytochemistry has become an increasingly used tool in the diagnosis of malignant endothelial tumors or tumors of an alleged vascular nature. In surgical pathology the most frequently applied markers are anti-Factor VIII-related antigen (anti-FVIII-R:AG) and Ulex europeus I agglutinin (UEA I) because of their ability to work on routinely formalin-fixed paraffin-embedded tissue. However, these markers label angiosarcomas inconstantly, which has prompted the search for more reliable markers, especially monoclonal antibodies specific for endothelial cell specific antigens. BMA 120 (formerly designated BW 200) is an endothelial cell specific monoclonal antibody detecting an epitope of a formalin resistant antigen. This marker labels a considerable number of angiosarcoma cells and it was compared with the staining patterns of anti-FVIIIR:Ag and UEA I in 19 angiosarcomas. Special regard was given to the distribution of antibodies in different parts of angiosarcomas.