Porphyromonas gingivalis lipopolysaccharide (Pg LPS) is an important virulence factor in chronic periodontitis. The aim of this study was to compare the expression of inflammatory cytokine genes in Escherichia coli LPS (Ec LPS) and Pg LPS-stimulated mouse macrophage RAW 264.7 cells. Cells were treated with Ec LPS and Pg LPS for 18 hours, and the cytokine gene expression profile was assessed using microarrays and confirmed by real-time PCR. Microarray analysis showed that both types of LPS induced a significant increase in the expression of IL-17β, IL-2, Ccl4, Cxcl2 and TNFα compared with the control. However, LT-b was up-regulated by Pg LPS but not by Ec LPS. Real-time PCR analysis of these genes showed similar results for LT-b, Ccl4, Cxcl2, and TNF- but found that IL-17β and IL-2 were upregulated by Pg LPS but not by Ec LPS. These data indicate that Pg LPS stimulates the transcription of IL-$17β}, IL-2, Ccl4, Cxcl2, LT-b, and TNFα, all of which may be involved in the pathogenesis of chronic periodontitis.