The identification of DNA variation or gene mutations, which contributes to or determines a disease, has been a major research focus, as it describes the underlying inherited disease components. With the human genome being sequenced, the reference sequence is now at hand, facilitating the systematic identification of DNA variation and its subsequent correlation to health and disease. The most common form of genetic variation in the human genome is a simple change of a basepair, a single-nucleotide polymorphism (SNP). In order to elucidate which SNPs might determine a disease as well as diagnosti-cally type those that already have a disease association, there is a substantial need for genotyping assays that are rapid, reliable, and cost-effective. In this chapter, we describe the various areas in which SNPs will be used as well as an overview of some of the most commonly used SNP genotyping methods.