This invention provides a therapeutic agent for inhibiting neovascularization, a therapeutic agent for a solid cancer, a therapeutic agent for a disease pathologically caused by neovascularization, and a therapeutic agent for repairing a tissue comprising as the effective ingredient, a substance that potentiates the action of CXCR4.Based on the finding that vascularization is suppressed in CXCR4 knockout mice, it becomes possible to prepare a therapeutic agent for suppressing vascularization, a therapeutic agent for a solid cancer, a therapeutic agent for a disease pathologically caused by neovascularization, each of which comprises as the effective ingredient, a substance that inhibits the action of CXCR4, as well as to prepare a therapeutic agent for repairing a tissue comprising as the effective ingredient, a substance that potentiates the action of CXCR4. Methods for treatment are made possible that use these therapeutic agents.