An increasing body of evidence supports the concept that host-produced PGE2 mediates much of the tissue destruction that occurs in periodontal disease. PGE2 levels within the crevicular fluid can serve as a static assessment of ongoing disease activity; i.e., rate of attachment loss and bone resorption. New insights into the mechanisms that regulate PGE2 synthesis provide an altered paradigm of periodontal disease which places the emphasis on host response, rather than the bacterial etiology, as the principal determinant of disease expression. We described a PGE2 host response model as a hypothetical framework to discuss new, possible explanations for host susceptibility to periodontal disease.