Abstract: The present invention provides a substance which inhibits binding of a signal transduction molecule to 1175-tyrosine phosphorylated KDR/Flk-1 and inhibits cell growth by VEGF. Also, the present invention provides a method for inhibiting KDR/Flk-1 signal transduction, a method for inhibiting cell growth, a method for inhibiting angiogenesis, a method for screening a cell growth inhibitor, a method for screening an angiogenesis inhibitor, a method for screening a substance which inhibits KDR/Flk-1 signal transduction, a method for determining whether or not a tested substance can inhibit KDR/Flk-1 signal transduction, a method for detecting angiogenesis in tissue and a method for screening a substance which inhibits 1175-tyrosine phosphorylated KDR/Flk-1, in which each method comprises using the substance.