Protein Folding aims to collect the most important information in the field of protein folding and probes the main principles that govern formation of the three-dimensional structure of a protein from a nascent polypeptide chain, as well as how the functional properties appear. This text is organized into three sections and consists of 15 chapters. After an introductory chapter where the main problems of protein folding are considered at the cellular level in the context of protein biosynthesis, the discussion turns to the conformation of native globular proteins. Definitions and rules of nomenclature are given, including the structural organization of globular proteins deduced from X-ray crystallographic data. Folding mechanisms are tentatively deduced from the observation of invariants in the architecture of folded proteins. The next chapters focus on the energetics of protein conformation and structure, indicating the principles of thermodynamic stability of the native structure, along with theoretical computation studies of protein folding, structure prediction, and folding simulation. The reader is also introduced to various experimental approaches; the reversibility of the unfolding-folding process; equilibrium and kinetic studies; and detection and characterization of intermediates in protein folding. This text concludes with a chapter dealing with problems specific to oligomeric proteins. This book is intended for research scientists, specialists, biochemists, and students of biochemistry and biology.