Background:This study was done to know the distribution and frequencies of blood groups among blood donors attending voluntary blood donation camps organized by the Rajendra Institute of Medical Sciences (RIMS), Ranchi, Jharkhand so that demand and supply ratio of the four blood groups can be maintained so that no patient dies due to lack of a particular blood group.Context:Up till now about 400 red cells antigen have been identified. The majority follow Mendelian inheritance. The ABO and Rhesus (Rh) blood group system are most important for blood transfusion purposes, parental testing, legal medicine, and in population genetic study.Aims:This study was conducted to determine and compare the frequency and distribution of ABO and Rh blood groups among voluntary blood donors attending blood donation camps in Jharkhand organized by RIMS. The aim is to know the demand and supply ratio of a particular blood group in light of their distribution in the society so that no patient dies due to the deficient supply of blood.Settings and Design:It is a retrospective study carried out at blood bank. Materials and Methods: A study was conducted at Blood bank, RIMS, Ranchi, Jharkhand, over a period of 4 years from January 1, 2012, to December 31, 2015. Blood group of the blood donors was determined by commercially available standard monoclonal antisera by test tube agglutination technique accompanied by reverse grouping.Results:Out of 20,455 subjects, 18,717 (91.73%) were male and 1738 (8.27%) were female subjects. The ABO blood group present was B (35.15%) followed by O (34.73%), A (22.09%), and AB (8.03%) in blood donors while in Rh system, (96.46%) donors were Rh +ve and (3.54%) donors were Rh −ve. The study has a significant implication regarding the inventory management of blood bank and transfusion services for the indoor patients of RIMS and for emergency supply to other hospitals of Jharkhand in dire need of blood.Conclusions:The knowledge of distribution of blood group is very important for blood banks and transfusion services which play an important role in the patient's health care. This study will also throw light on the reasons of deficiency of a particular group in a particular area so that deficient group donors may be encouraged to donate more frequently.