With the molecular basis of P1PK blood group system (previously named P blood group system) was identified recently, all the molecular background of 30 blood group systems were elucidated. Knowledge of the molecular backgrounds of these genes enable us to predict blood group phenotype from gDNA. Compared to serologic assays, DNA testing is more precise and overcomes some limitations of serologic assays, for example, accurate typing of red blood cells (RBCs) in multiply transfused, transfusion-dependent patients and antibody identification. To date, molecular testing has been widely used in genotyping blood group antigens and has become an indispensable tool in the specialized immunohematology laboratories. Most of the blood group antigens polymorphisms are determined by single nucleotide polymorphisms (SNPs); SNPs of red cell blood group antigens can be determined by the polymerase chain reaction with sequence specific priming (PCR-SSP) assay.