PURPOSE: Choroidal neovascularization (CNV) is the leading cause of blindness in patients with age-related macular degeneration (AMD). This study evaluated the inhibitory effect of vasostatin (VS), an endogenous angiogenesis inhibitor, on CNV. METHODS: Anti-angiogenic activity of VS was evaluated in vitro by migration and tube formation assays in human umbilical vein endothelial cells (HUVECs). CNV lesions were induced in Brown Norway rats by fundus argon laser photocoagulation. Beginning one day after CNV induction, rats were treated with eye drops containing 1 microg/ml VS in PBS buffer for three times daily for 20 days. The extent of CNV was examined by flat mount analysis on day 24 or by fundus fluorescein angiography (FAG) on days 21, 28, 35, and 42, respectively. CNV lesions and choroidal vascularity were evaluated by histological analysis. The spatial distribution of topically applied VS in rat eyes was evaluated by immunoblot analysis. RESULTS: VS inhibited migration and tube formation in HUVECs. Flat mount analysis revealed that, after laser-induced photocoagulation, topical VS application for 20 days significantly reduced CNV lesions. Moreover, serial FAG analysis indicated that a 20 day VS treatment significantly reduced CNV lesions on all subsequent days. Histological analysis revealed attenuated lesions, intact Bruch's membrane, and reduced choroidal vascularity in VS-treated eyes. Finally immunoblot analysis reveled VS expression in choroids. CONCLUSIONS: Topical VS application suppresses the progression of laser-induced CNV via angiogenesis inhibition and may constitute a therapeutic alternative for excessive neovascularization occurring with ocular diseases.