Three major neutrophil chemotactic peptides belonging to the interleukin-8 (IL-8) family were purified to homogeneity from the conditioned medium of the IL-1 beta-stimulated human gingival fibroblasts culture. On the basis of their molecular masses and NH2-terminal amino acid sequences, these three neutrophil chemotactic factors were identical to melanoma growth stimulatory activity-alpha (MGSA/gro-alpha), MGSA/gro-gamma and Ala-Val-Leu-Pro-Arg-IL-8 (AVLPR-IL-8), each belonging to the IL-8 family. It has been shown by the chemotaxis studies in vitro that the chemotactic activity of MGSA/gro-gamma is similar to that of MGSA/gro-alpha for both human and rat neutrophils, while AVLPR-IL-8 is chemotactic for human neutrophils but not for rat neutrophils. The in vitro findings were supported by the histological studies in vivo on the intradermal injection of either MGSA/gro-alpha or AVLPR-IL-8 into the back of the rats. The results obtained in the present experiment suggest that human gingival fibroblasts play an important role in gingival inflammation through the production of neutrophil chemotactic factors newly characterized as the IL-8 family in response to inflammatory chemical mediators including IL-1 beta.