Neomycin has been shown to block nuclear translocation of angiogenin in endothelial cells, thereby inhibiting its capacity to induce angiogenesis. We report here that neomycin is also an effective inhibitor of angiogenesis induced by acidic fibroblast growth factor, basic fibroblast growth factor, and epidermal growth factor, all of which undergo nuclear translocation, but not that of vascular endothelial growth factor which does not undergo nuclear translocation. Blocking nuclear translocation, therefore, seems to be a general mechanism for the antiangiogenesis action of neomycin applicable to those angiogenic factors that require nuclear translocation for angiogenesis. These results along with the known toxicity and phamacokinetics profiles make neomycin and its analogues good candidate inhibitors of angiogenesis that might be developed as antitumor agents.