In the few years since the first edition of this book made its appearance, under­ takings in the area of protein sequence determination have increased at an almost logarithmic pace. The logic governing such efforts has, predictably, retreated from a simple sense of curiosity in achieving something that had not previously been done, to be replaced by an absolute requirement for sequence information as the best means for understanding heretofore unattainable aspects of chemical, and structural and functional mechanistic phenomena. Witness, for example, recent volumes of the Annual Review of Biochemistry and other review journals, which treat the genetic control of mitochondrial proteins, mechanisms of enzyme action, the immunochemistry of collagen, and the role of lysosomal enzymes in the lipid storage diseases - all on the basis of known protein sequence information. One must note, too, the appearance of related works in the area of nucleic acid sequencing. The technologic advances in chemical sequencing procedures have proliferated at a remarkable rate. It is in the area of instrumentation, however, that the greatest advances have taken place. As a consequence of this, each chapter (with one single exception) in this book has been extensively revised and updated. Entire chapters have been replaced in several cases, without minimizing the value of their original content. In addition, a second volume will appear soon, dealing with subjects not covered in the present book.