 Patients will be sequentially enrolled, administered a loading dose of 15 mgkg bevacizumab intravenously on day 1, and then administered 15 mgkg bevacizumab intravenously every 3 weeks beginning one week after the loading dose. The drug will be temporarily discontinued for toxicity, intercurrent major surgical procedures, or other factors that would pose a safety concern. Patients will undergo a biopsy of a KS lesion at entry, on cycle 4, day 21, and at the time of a formal response or when the patient stops treatment. Patients will undergo a number of other tests as well, including blood tests and non-invasive imaging studies of KS lesions. 