Chemokines are small proteins that control cellular migration. An extensive family of these molecules has been described in mammals containing nearly 50 members. Within this family are four groups, each defined by the different spacing of two N-terminal cysteines, which form disulphide bonds with two other cysteine residues to create the tertiary structure characteristic of chemokines. Recent evidence shows the chemokine family is not unique to mammals, with several members also identified in birds, amphibians and fish, including a primitive vertebrate, the lamprey. Although there is less evidence to define the roles of chemokines in these lower vertebrates, structural similarities allow some predictions to their function, against which further studies are being made. Additionally, some microorganisms (particularly viruses) appear to have copied genes for chemokines, presumably to confuse the immune system of their host. This review aims to bring together the current information concerning identified chemokines throughout vertebrates and microorganisms.