Introduction: Determination of blood groups is the first step in the approval or rejection of blood relation
between the two individuals for identity recognition. The aim of this study is to investigate the reliability of common blood grouping systems in DNA finger printing recognition.Methods: In this study, blood samples were obtained from 300 individuals belonging to 150 families. Then, DNA of each individual was purified and DNA finger printing was performed for 10 STR regions using ABI set. Seven human blood group systems including ABH, RH, Kidd, Kell, Mns, Lutheran and p1 were determined with agglutination methods, and the results were compared with DNA sequencing results of the ABI sequencing machine.Results: 300 randomly selected individuals were studied, in 256 cases. There was no difference between the blood grouping and DNA typing results; in 44 cases, the blood relation was approved by DNA typing but antigenic discord was observed in RH, MNS and ABH antigens. Among the blood grouping systems, RH, MNS and ABH,with the error scale of 30.7% (P=0.001), 20.54% (0.04) and 17.6% (P=0.005) respectively, were found to be the weakest systems for human identity recognition.Conclusion: Among the blood grouping systems, RH, MNS and ABH are the weakest markers for blood relation identification, and DNA finger printing must be used as a supplementary test to confirm their results.