The identification of a biological species from an unknown material can be performed using a mitochondrial DNA locus. The cytochrome b (cyt b) gene is one of the most commonly used genetic loci, applied in both taxonomy and forensic science, for the purpose of species identification. The gene is 1,140 basepairs long in most vertebrates and shows little intraspecies variation, but sufficient interspecies variation. The gene is too long for typical PCR-based methods and, as many samples are degraded, only a section of the locus is used. DNA sequences at the start of the gene became the favored section for phylogenetics and species identification. The DNA sequences from any unknown sample from this part of the cyt b gene can be determined and compared to those on a DNA database to determine the most likely species from which the unknown sample originates. The process of DNA amplification, sequencing, sequence comparison, and identification form the basis of this chapter.