We cloned a 2.3-kb sequence homologous to the gene (hIL8) encoding human interleukin-8 (hIL-8) from the canine genome. The sequence may encode an 11.3-kDa protein consisting of 101 amino acids, sharing 75, 80 or 85% identity with the human, rabbit or porcine IL-8 proteins, respectively. Southern and Northern blot analyses indicated that the cloned sequence appeared to exist as a single copy in the canine genome, and that its expression was inducible with lipopolysaccharide in canine mononuclear cells, respectively. Thus, it seems very likely that the cloned gene is a canine homologue of hIL8.