Proteins are the molecules of choice when highly specific medical treatments or other highly specific technical properties are required. The first chapters provide an overview of protein structure and function and of the design and uses of recombinant proteins. Options and issues of antibody therapies are discussed in chapters ranging from the design and manufacture of antibodies through pre-clinical testing and clinical development. The new approach to treatment of disease by targeted gene therapy is reviewed demonstrating the extent of challenges still to be met before gene therapy products can be used successfully. The rapidly changing global regulatory environment and pharmacoeconomic issues for products of biotechnology are also highlighted.