Periodontitis is primarily caused by bacteria. However, the host immune response may influence the inflammation severity of disease. Many studies on the relationship between interleukin-1 β and periodontitis conclude that interleukin-1 is one of pro-inflammatory cytokines contributing to periodontal destruction. Researchers have recently investigated the role of genetic factor in the periodontitis, and found that interleukin-1 gene exists in polymorphous type.. This article introduces interleukin-1 gene polymorphism, its variety among different races, and the impact of interleukin-1 gene polymorphism on the amount of interleukin-1 secretion, as well as the relevance of the severity of periodontitis to the outcome of periodontal treatment.