Biomarkers are molecules that can be objectively measured and evaluated as indicators of normal biological processes, pathological processes or pharmacological responses to therapeutic intervention. In the crevicular gingival fluid, biomarkers have been studied as host proteins including enzymes, immunoglobulins, interleukins, cytokines, chemokines and prostaglandins, which could be helpful in evaluating periodontal diagnosis and treatment outcomes, as well as monitoring patients at risk of develop periodontitis. The purpose of this review is to show some of the most studied biomarkers in periodontal disease.