The objective of the study was to determine the relationship between ABO blood groups and diabetes mellitus in the population of Pune, Maharashtra [India]. The present study included analysis of  ABO blood group. The data of blood group obtained among 500 subjects of every age taken randomly from the local population of Pune city in the duration of Sept 2014 to February 2015. Out of that 359 were male and 141 were female patients suffering Diabetes Mellitus. From present study it is concluded that there is relativity in between blood groups & diabetes mellitus. The association exists between blood group B + ve   and Diabetic Mellitus. The result of study shows that 50 % of diabetic patient having B +ve blood group. In this study, frequency of ABO blood groups observed was in an order of B +ve > A +ve > O +ve > AB +ve > B -ve.> A -ve