Success in Recombinant DNA technology has been possible due to rapid development in gene cloning methodologies. It is essentially the insertion of a specific fragment of foreign DNA into a cell, through a suitable vector, in such a way that inserted DNA replicates independently and transferred to progenic as a result of cell Division. The transformed cells containing DNA after their characterizations and confirmation can be used commercially for the production of useful compounds such as insulin, interferon, growth hormones, etc. The book is divided into 21 chapters. The language pf book is simple, easily understandable and subject matter is fully illustrated. This book will be useful for undergraduate and postgraduate students in molecular biology and biotechnology courses.