Kaposi's sarcoma (KS) is the most common tumor among HIV-infected individuals, but its involvement in the gastrointestinal tract was reported long before the AIDS epidemic. Although most cases of gastrointestinal KS are asymptomatic, advanced lesions may occasionally result in a severe and life-threatening hemorrhage that requires immediate treatment. At the NYU Medical Center, we have seen three AIDS patients present with severe upper tract bleeding (> 8 U/48 h) from KS lesions of the antrum, fundus, and duodenum. The last patient was also bleeding from an ulcerated rectal KS lesion. Because all three patients had a coexisting thrombocytopenia (platelets < 50,000/mm3) and were poor operative risks, injection sclerotherapy was performed. All four KS lesions stopped bleeding, and three out of the four lesions decreased in size. To our knowledge, this is the first report of successfully using sclerotherapy to treat severe hemorrhage due to gastrointestinal KS.