Recombinant DNA technology is a technique which changes the phenotype of an organism (host) when a genetically altered vector is introduced and integrated into the genome of the organism. So, basically the process involves the introduction of a foreign piece of DNA structure into the genome which contains our gene of interest. This gene which is introduced is the recombinant gene and the technique is called the recombinant DNA technology. Inserting a desired gene into the genome of the host is not as easy as it sounds. It involves the selection of the desired gene for administration into the host followed by a selection of the perfect vector with which the gene has to be integrated and recombinant DNA formed. This recombinant DNA then has to be introduced into the host. And at last it has to be maintained in the host and carried forward to the offsprings. In molecular cloning, a vector is a DNA molecule used as a vehicle to artificially carry foreign genetic material into another cell, where it can be replicated and/or expressed (e.g.- plasmid, cosmic, Lambda phages). A vector containing foreign DNA is termed recombinant DNA. The four major types of vectors are plasmids, viral vectors, cosmids, and artificial chromosomes. Of these, the most commonly used vectors are plasmids. Common to all engineered vectors are an origin of replication, a multicloning site, and a selectable marker. Recombinant DNA Technology is focuses on the current state of knowledge on recombinant DNA technology and its applications. The book will provide comprehensive knowledge on the principles and concepts of recombinant DNA technology or genetic engineering, protein expression of cloned genes, PCR amplification of DNA, RFLP, AFLP and DNA fingerprinting and finally the most recent siRNA technology. It can be used by post-graduate students studying and teachers teaching in the area of Molecular Biology, Biotechnology, Genetics, Microbiology, Life Science, Pharmacy, Agriculture and Basic Medical Sciences.