To avoid the well-known shortcomings of phenotyping granulocytes for the NA antigens using NA-specific human sera, a DNA-based method to determine the NA genotype was developed. Genomic DNA was isolated from blood cells or serum, amplified by polymerase chain reaction (PCR), immobilized on nylon membrane and genotyped using digoxigenin-labeled, sequence-specific oligonucleotides (SSO). The genotyping results of whole blood samples from 54 and of serum from 20 individuals correlated perfectly with our phenotyping using the antigen capture assay MAIGA. In three cases with the phenotype "NA-null" no hybridization of the NA-specific oligonucleotides occurred. These data show that SSO is a reliable method for NA genotyping especially if only small volumes of blood or even only serum probes are available.