BackgroundThe development of periodontal diseases has multifactorial causes including genetic factors. Limited investigations have been conducted to explore the association between ABO blood groups and the development and progression of periodontal diseases. AimTo evaluate and assess the association of ABO Phenotype and Rhesus factor with oral hygiene status, severity of chronic periodontitis and blood parameters like hemoglobin level and Platelet count in localized and generalized chronic periodontitis. Material and methodsStudy was carried out on 100 patients, out of which 80 patients of Generalized Chronic Periodontitis and 20 patients of Localized Chronic Periodontitis. Patients were categorized into Mild, Moderate and Severe Periodontitis. ResultA highly significant association was found between severity of periodontitis and blood groups with blood group B and O were found to be at a greater risk to develop moderate to severe form of chronic periodontitis. Also subjects with blood group B and O showed worst oral hygiene among all the blood groups. Also patients suffering from chronic periodontitis showed a general trend towards lower limit of both hemoglobin level and platelet. ConclusionGenetic factors such as ABO blood group antigens may act as a risk influencer that plays a role in progression and severity of the chronic periodontitis, with blood group B and O being worst affected. Another observation was that a long standing case of chronic periodontitis can lead to anemia thus having systemic implications.