The recruitment of leukocyte populations to an area of inflammation is one of the most fundamental processes of immune reactivity, yet a number of the mechanisms which are important to this process are not clearly understood. Investigations directed at understanding the mechanisms of leukocyte elicitation have centered around classical chemotactic factors such as C5a and fMLP, however, these known agents have demonstrated little specificity for recruiting particular leukocyte populations. Recent advances in this field have been made with the discovery of a novel supergene family of chemotactic cytokines or chemokines. These cytokines are important as they possess a high degree of specificity for the recruitment of specific subpopulations of leukocytes.