Aim: The aim of the present study was to investigate the effects of LPS on the production of chemokines and cytokines in periodontal ligament cells (PDL cells) and if LPS affects functional characteristics of the cells, such as alkaline phosphatase (ALP) activity, collagen and DNA-synthesis. We also assessed if estrogen modulated the LPS-induced responses. Material and Methods: Explants were obtained from the middle third of root surface from teeth extracted for orthodontic reasons. Cells were allowed to migrate from explants and were used in passages 3-4. Aortic tissue was obtained from NMRI mice. Production of monocyte chemoattractant protein-1 (MCP-1), IL-6 and C-reactive protein (CRP) were assessed using ELISA. Transcriptional activity of macrophage inflammatory protein-2 (MIP-2) gene was examined using real-time RT-PCR. ALP activity was measured using a substrate solution and read colormetrically. Collagen and DNA-synthesis were measured using the radiolabeled isotopes proline and thymidine, respectively. The measurements were corrected to the total amount of protein according to the Lowry method. Results: LPS enhanced the production of MCP-1 and IL-6 in PDL cells in a time and dose dependent manner, but had no effect on CRP production. The effects of LPS in PDL cells were not reversed by estrogen. LPS did not affect ALP activity, collagen and DNA-synthesis in PDL cells. LPS enhanced the transcriptional activity of MIP-2 in smooth muscle cells (SMCs). LPS induced MIP-2 was attenuated by a physiological concentration of estrogen (100nM). Conclusion: LPS enhances the production of MCP-1 and IL-6 in PDL cells in a specific manner. LPS induced MCP-1 production in PDL-cells suggests an important role of PDL cells in recruiting leucocytes to the periodontal ligament. Down-regulation of MIP-2 gene by estrogen suggests that estrogen exerts an anti-inflammatory effect via this mechanism.