The reception of the original volume by students, pedagogues, and reviewers has been most gratifying. It appears to have both satisfied a need and served a useful educational purpose. Hence, some ten years later it has been deemed advisable to bring it up to date, if only in a slightly expanded form. The purpose for writing this book and its level remain the same. Many new polymers have been synthesized in the last decade that have found meaningful and novel uses. Examples of these applications are included in this new edition. Major advances have also been made in biophysics and in molecular biology, as well as in our understanding of natural processes on a molecular level. Foremost among these has been the development of recombinant DNA technology. With it has come the potential for large scale synthesis of hormones and proteins. These new developments have also been incorporated into the present volume. It is my hope that this new edition will still have a widespread appeal to students in all of the natural sciences whatever their major interest. It should also be of use and inter est to those starting industrial or academic careers who have not had an extensive background in macromolecular science.