We have found that two chemokines, recombinant gro-alpha and gro-beta, specifically inhibit growth factor-stimulated proliferation of capillary endothelial cells in a dose-dependent manner, whereas gro-gamma has no inhibitory effect. In vivo, gro-beta inhibits blood vessel formation in the chicken chorioallantoic membrane assay. It is sufficiently potent to effectively suppress basic fibroblast growth factor-induced corneal neovascularization after systemic administration in mice. Further, gro-beta significantly inhibits the growth of murine Lewis lung carcinoma in syngeneic C57B16/J and immunodeficient nude mice without toxicity. In vitro, Lewis lung carcinoma cells are completely insensitive to recombinant gro-beta at high concentrations that significantly inhibit endothelial cell proliferation. This finding supports the conclusion that gro-beta inhibits Lewis lung tumor growth by suppression of tumor-induced neovascularization.