Genotyping is useful to predict the expression of those RBC antigens for which antisera are difficult to obtain and to determine the probable phenotype of highly transfused patients, and it can be used to test stored DNA when a blood sample is not available. This study assessed a sequence-specific primer (SSP)-based genotyping system for blood group alleles suitable for the rapid testing of a small number of samples and assessed the use of stored whole blood. Genomic DNA was isolated from fresh and 1- and 2-week-old stored blood from 20 donors with known ABO and Rh phenotypes and was used for