OBJECTIVE Alternatives to cytotoxic agents are desirable for patients with HIV-associated Kaposi's sarcoma (KS). Vascular endothelial growth factor-A (VEGF-A) contributes to KS pathogenesis. We evaluated the humanized anti-VEGF-A monoclonal antibody, bevacizumab, in patients with HIV-KS. METHODS Patients with HIV-KS who either experienced progression while receiving highly active antiretroviral therapy (HAART) for at least 1 month or did not regress despite HAART for at least 4 months were administered bevacizumab 15 mg/kg intravenously on days 1 and 8 and then every 3 weeks. The primary objective was assessment of antitumor activity using modified AIDS Clinical Trial Group (ACTG) criteria for HIV-KS. HIV-uninfected patients were also eligible and observed separately. RESULTS Seventeen HIV-infected patients were enrolled. Fourteen patients had been receiving effective HAART for at least 6 months (median, 1 year). Thirteen patients had advanced disease (ACTG T(1)), 13 patients had received prior chemotherapy for KS, and seven patients had CD4 count less than 200 cells/μL. Median number of cycles was 10 (range, 1 to 37 cycles); median follow-up was 8.3 months (range, 3 to 36 months). Of 16 assessable patients, best tumor responses observed were complete response (CR) in three patients (19%), partial response (PR) in two patients (12%), stable disease in nine patients (56%), and progressive disease in two patients (12%). Overall response rate (CR + PR) was 31% (95% CI, 11% to 58.7%). Four of five responders had received prior chemotherapy for KS. Over 202 cycles, grade 3 to 4 adverse events at least possibly attributed to therapy included hypertension (n = 7), neutropenia (n = 5), cellulitis (n = 3), and headache (n = 2). CONCLUSIONS Bevacizumab is tolerated in patients with HIV-KS and has activity in a subset of patients.