In this study, the aim was to find out the prevalence of blood groups in a group of patients in World College of Medical Sciences & Research and Hospital, Jhajjar, Haryana, India. In this study, the blood groups of 612 patients were evaluated. In this study, the results showed that the prevalence of different blood groups among one group of 612 patients was approximately: B+ 36%, O+ 28%, A+ 19%, AB+ 8% and Rh negative- 9 % (O- 4%, B- 3%, A- 1% & AB- 1%). Thus, B+ is the most common blood group in our study. By conventional criteria, this difference was considered to be extremely statistically significant. It is also concluded that the B gene is the most frequent, about 39% (B+ 36% & B- 3%), followed by O gene (O+ 28% & O- 4%), whereas the A gene is infrequent, in the present study.