Periodontal disease is a multifactorial disease. It comprises a variety of conditions affecting the health of the periodontium. Clinical models of disease activity in patient suffering from periodontitis range from a continuous progression of disease which causes loss of attachment at a slow rate for a longer period, to an episodic burst model which causes loss of attachment at a rapid rate in a short period of time.If left untreated, it leads to further alveolar bone destruction, increased tooth mobility and subsequent tooth lossTraditional diagnostic procedures deal with history and severity of periodontal disease but does not tell about the current disease status. Hence, recent advances in oral and periodontal disease diagnosis are moving toward methods that can identify periodontal disease susceptibility, active sites and individual's response to periodontal therapy by measuring the levels of 'BIOMARKERS'. This book is the literature review on various biomarkers in periodontology and their role in the diagnosis of periodontal diseases and monitoring treatment outcome.