Back ground: The ABO and Rhesus –D blood group are the major blood group systems. The frequency of four main blood group systems varies in population throughout the world and even in different parts of the country. ABO & Rh blood group antigens play a Vital role in immunologic safety of whole blood and blood component transfusion and also useful in population genetic studies, in resolving medico legal issues. Aim: This study is aimed to document the frequency and distribution pattern of ABO and Rh among blood donors in S.V.R.R.Govt. General Hospital, Tirupati. Study Design: It is a retrospective record based study carried out at Model blood bank S.V.R.R.Govt. General Hospital Tirupati from January 2014 to December 2015. Material and Methods: The study was conducted on 13,040 donors. ABO and Rh typing was done by using slide agglutination method with antisera ABO and Rh (tulip Diag). Doubtful cases were confirmed by tube agglutination method and reverse grouping by using pooled A& B cells. The age group and sex of donors and frequency of ABO and Rh blood groups were reported in simple percentages. Results: In the present study the most common blood group was ‘O’ 5505 (42.2%) and least common being AB 778 (5.96%). The prevalence of Rh positive and negative distribution in the study population is 12267(94.07%) and 773(5.93%) respectively. Predominant donors belonged to age group between 18-35 years (85.37 %).Male donors (97.88%) are common than female donors (2.12%) with ratio. Blood group frequency with respect to ABO and Rh was found to be O>B>A>AB. Conclusion:   O positive blood group is significantly high  in our population  while AB Iis least.. Blood donation by females appears to be low provably because of illiteracy, malnutrition and social taboo. So female donor need to be motivated for blood donation.  Knowledge of frequencies of different blood groups is very important for blood banks and transfusion service polices for better use and good inventory of blood units. Key words: Blood groups ABO, Rh