Matrix metalloproteinase (MMP) are the key enzymes in matrix degradation, as these endopeptidases act synergistically to degrade the proteins which form remodelling of periodontal tissues in health. However in disease the balance between matrix metalloproteinases and its inhibitors is lost and matrix metalloproteinase levels increase compared to its inhibitors. In various studies under taken it has shown that this balance can be restored by treatment which removes the factors, which induce MMP production and also by the use of drugs which act on factors which regulate MMP production, release & activity e.g. CMTs. Also MMP & its inhibitor levels in saliva, GCF and gingival tissues have been assessed, and cells producing these enzymes have been immunolocalised with the present available knowledge about MMPs and its inhibitor, it can be concluded that the amount, type, source and activity of these enzymes in saliva, gingival crevicular fluid and gingival tissues may help us to diagnose the type of periodontitis, their likely response to therapy and may help in monitoring the course of the disease.