A variety of factors have been identified that regulate angiogenesis, including the CXC chemokine family. The CXC chemokines are a unique family of cytokines for their ability to behave in a disparate manner in the regulation of angiogenesis. CXC chemokines have four highly conserved cysteine amino acid residues, with the first two cysteine amino acid residues separated by one non-conserved amino acid residue (i.e., CXC). A second structural domain within this family determines their angiogenic potential. The NH₂ terminus of the majority of the CXC chemokines contains three amino acid residues (Glu-Leu-Arg: the ELR motif), which precedes the first cysteine amino acid residue of the primary structure of these cytokines. Members that contain the ELR motif (ELR⁺) are potent promoters of angiogenesis. In contrast, members that are inducible by interferons and lack the ELR motif (ELR⁻) are potent inhibitors of angiogenesis. This difference in angiogenic activity may impact on the pathogenesis of a variety of disorders.