Abstract: Association between certain systemic diseases and ABO blood group is a well known fact. The purpose of this study was to determine whether there is any association between periodontal disease and ABO blood groups. A cross sectional study was carried-out on 200 subjects who were randomly selected from individuals referred for periodontal treatment. The study subjects were segregated into healthy gingiva/mild gingivitis (Group I), moderate/severe gingivitis (Group II) and varying grades of periodontitis groups (Group III) , based on Loe and Silness index and clinical attachment loss as the criteria. The study groups were further categorized and graded using Ramfjord's periodontal disease index. Blood samples were collected to identify ABO blood groups. A non-parametric test, Chi-square test, was used for statistical analysis. Patients with blood group O and B were more pre-disposed to develop periodontitis with at least one side with attachment loss of more than 3 mm and with periodontal pocket depth of more than 4 mm with statistically significant results (p<0.001). There is a correlation existing between periodontal disease and ABO blood groups as far as this region was concerned. This association could be explained by the various blood group antigens acting as receptors for infectious agents associated with periodontal diseases. This broad correlation between periodontal disease and ABO blood groups pointed towards susceptibility of the subjects with certain blood groups to periodontal diseases.