Interleukin 8 (IL-8) is one of the most widely studied chemoattractants for leukocytes. It belongs to the newly classified CXC family of chemokine which possesses biological activities mainly on neutrophils. The potential role of IL-8 in inflammation is substantiated by the growing evidences of clinical relevance of IL-8 in various diseases such as infection, ischemia and autoimmune disorders. The common characteristic pathological feature of these events is neutrophil infiltration. Although little is known about the mechanism of neutrophil recruitment into the urine, urinary tract infections (UTI) are accompanied by pyuria. Elevated urinary IL-8 levels were found in patients with UTI. Bioactive, multiple forms of IL-8 were produced locally within the urinary tract, and implied that IL-8 participated in the induction of neutrophil migration into the inflammatory site. Similar findings were observed in the peritoneal dialysate of patients on continuous ambulatory peritoneal dialysis with peritonitis. The notion of involvement of IL-8 in local infection was reinforced by the findings obtained on the rabbit UTI model. Finally, the clinical usefulness, as well as the problems of IL-8 level determination in various body fluids are discussed.