Adult periodontitis (AP) is a chronic inflammatory disease whose etiology is not well defined. Some studies suggested that the clinical characteristics of this disease may be in part explained by genetic factors, and some attempts to find genetic markers for this disease were successful. The interleukin-1 (IL-1) gene family as one of genetic factors may influence the expression of adult periodontitis. The aim of present study is to investigate the frequencies of genetic polymorphisms in the IL-1 gene family encoding three genes (IL-1A, IL-1B and IL-1RN) in Korean AP patients and periodontically healthy controls. There were no significant differences in genotype and allele frequencies of these polymorph isms between two groups, respectively. However, -511 polymorphism of IL-1 B gene was significantly associated with mean pocket depth (MPD, mm) value in AP patients (P<0.05). Therefore, our results suggest that -511 polymorphism in the IL-1B gene may be useful as a genetic marker for the severity of AP in Koreans.