Single nucleotide polymorphisms (SNPs) are emerging as new markers of interest to the forensic community because of their abundance in the human genome, their low mutation rate, the opportunity they present of analyzing smaller fragments of deoxyribonucleic acid (DNA) than with short tandem repeats--important in degraded DNA samples--and the possibility of automating the analysis with high-throughput technologies. Many new technologies for genotyping SNPs have been developed in the past few years. We describe the principles of the allelic discrimination reactions and the technologies used for each of them. The aim of this chapter is to help in the understanding of the methodologies used in SNP genotyping and in the selection of the most appropriate techniques for forensic purposes.