In the early 1990s, almost 200 yr after Edward Jenner demonstrated the effectiveness of the smallpox vaccine, a new paradigm for vaccination emerged. The conventional method of vaccination required delivery of whole pathogens or structural subunits, but in this new approach, DNA or genetic information was administered to elicit an immunological response. Once it was observed that plasmid DNA delivered in vivo led to production of an encoded transgene (1), two ground-breaking studies demonstrated that immunological responses could be generated against antigenic transgenes via plasmid DNA delivered by DNA vaccination (as this approach is called) (2,3). The appe- ance of this new vaccination strategy coincided with advances in molecular biology, which provided new tools to study and manipulate the basic elements of an organism's genome and also could also be applied to the design and production of DNA vaccines. DNA Vaccines is a major updated and enhancement of the first edition. It reviews state-of-the-art methods in DNA vaccine technology, with chapters describing DNA vaccine design, delivery systems, adjuvants, current appli- tions, methods of production, and quality control. Consistent with the approach of the Methods in Molecular Medicine series, these chapters contain detailed practical procedures on the latest DNA vaccine technology. The enthusiasm for DNA vaccine technology is made clear by the number of research studies published on this topic since the mid-1990s.