Angiogenesis is important to a variety of physiological and pathological processes. While a variety of factors have been determined to regulate angiogenesis, members of the CXC chemokine family can either promote or inhibit this process. This disparity in biological behavior is due to the presence or absence of a structural-functional domain--three amino acid residues (Glu-Leu-Arg: the "ELR-motif") that precede the first cysteine amino acid residue of the primary structure of these cytokines. The purpose of this study is to introduce the topic of angiogenesis and focuses on the CXC chemokine family, because these cytokines are a unique family of molecules that can behave in a disparate manner in the regulation of angiogenesis associated with either chronic inflammatory-fibroproliferative disorders or tumor growth.