Backround: ABO and Rhesus (Rh) blood group antigens are hereditary characters and are useful in population genetic studies, in resolving medico-legal issues and more importantly for the immunologic safety of blood during transfusion. This study is aimed to determine the distribution pattern of the ABO and Rh blood groups among blood donors in Kumaon region of Uttarakhand and compare it with other data from similar studies within the India and all over the world. It is a retrospective study carried out at blood bank of Shushila Tewari Hospital of Government Medical College, Haldwani from January 2012 to December 2013. The study was conducted on 12,701 blood donors. ABO and Rh typing was done using slide agglutination method with antisera ABO and Rh (Tulip diagnostics ltd). Doubtful cases were confirmed by tube agglutination method and reverse grouping using known pooled A and B cells. The age group and sex of donors, frequency of ABO and Rh blood groups were reported in simple percentages. The predominant donors belonged to age group between 18-35years (84.28%). Male donors were more than female donors, ratio being 352:1. Replacement donors (99.71%) were much more than voluntary donors (0.91%). The most common blood group was B (32.07%) and least common being AB (10.53%). Blood group 'O' and 'A' had same frequency. The prevalence of Rhesus positive and negative distribution in the studied population was 94.49% and 5.51% respectively. Blood group frequency with respect to ABO and Rhesus positive was found to be shown by formula B> O>A >AB. The frequency for ABO and Rhesus negative was given by the formula B>A>O>AB. Knowledge of frequencies of the different blood groups is very important for blood banks and transfusion service policies that could contribute significantly to the National Health System.