Collagen is a fascinating protein not only because of its ubiquitous occurrence in multicellular animals, but also because of its unique chemi­ cal structure. As the predominant constituent in bone, cartilage, skin, tendon, and tooth, it is not surprising that collagen is of interest to anatomists, biochemists, biomedical engineers, cell biologists, dermatolo­ gists, dental surgeons, leather chemists, orthopedic surgeons, physiologists, physicians, zoologists, and a host of others. This book was planned to provide an up-to-date comprehensive survey of all aspects of biochemistry of collagen. The recent discovery of genetically distinct collagens with tissue specificity has opened a new era in collagen biochemistry, and Karl Piez discusses this in the opening chapter on primary structure. In the next chapter, Ramachandran and Rama­ krishnan deal with the molecular structure of collagen, placing special emphasis on the conformational aspects of its polypeptide chains. Follow­ ing the consideration of primary and secondary structure of collagen, the three-dimensional arrangement of collagen molecules in the fibrils is covered by Miller in Chapter 3. Collagen is generally in the insoluble state in the living organism due to the cross-linking of individual molecules, and Tanzer describes the various aspects of this cross-linkage in Chapter 4. The biosynthesis of collagen is discussed in depth by Prockop and his colleagues.