The illegal mislabeling of fish and seafood species can have detrimental effects on both the industry and the consumer. To prevent these effects, which include economic fraud and health hazards, a research priority has been the development of species authentication techniques that are rapid, reliable, and reproducible. These include methods based on either species-specific/multiplex PCR or post-PCR analysis methods such as DNA sequencing, RFLP, SSCP, RAPD, and AFLP. Numerous nuclear and mitochondrial genetic markers have also been examined, with the most prominent being the mitochondrial gene cytochrome b. While genetic differentiation techniques have been extensively researched among certain fish groups, including the gadoids, salmonids, and scombroids, many challenges still remain. These include the optimization of methods that use smaller fragments, which can be analyzed in both raw and processed products, and the identification and quantification of species in mixed samples. In response to these challenges, future trends point to the use of technologies such as DNA microarray chips and quantitative real-time PCR methods. Furthermore, the use of databases has become increasingly important in this field by providing a compilation of genetic information on a variety of fish and seafood species