Background of study: Apart from blood transfusion practice, knowing of the ABO and Rh blood groups are useful in population genetic studies, researching population migration patterns as well as resolving certain medico legal issues, particularly of disputed paternity cases and certain diseases. Objective: The present study aim is to determine the most commonblood groups for purpose of emergency blood transfusion and to comparewith other studies. Research Methodology: The observational cross sectional study was done at Department of Pathology at Great Eastern Medical School, Srikakulam, Andhrapradesh of South India during October 2012 to Februry 2013. Blood group of the Medical students was determined by commercially available standard monoclonal antisera .The sample blood was collected by finger prick method. A drop of monoclonal reagent anti A, anti B, and Anti D were added to a drop of blood on clean and fresh glass slides and mixed well with glass rod. Results of agglutination were recorded immediately. Results: During the observation, total number of subjects studied were175, among them 78 was males and 97 were females. Study showed Blood group O was more predominant in both males and Females. Conclusion : It was observed that in both male and females the most frequently occurring ABO blood group was O (46.9%), followed by B (29.7 %), A (17.1 %), and AB (5.1%). Rh positive seen in 94.9% of the students. Only 5.1 % of the students in our study group were Rh negative.