A continued interest in Peptide Chemistry prompted the revision of the first edition of this book. This provided an opportunity to update several details. I am grateful to colleagues who were kind enough to inform me of errors, typographical and other, they had discovered in the first edi­ tion. These have now been corrected, as were certain shortcomings in language and style pointed out by my daughter, Dr. Eva Bodanszky. In 1991 the excellent The Chemical Synthesis of Peptides by John Jones (Oxford University Press, 1991) appeared. It covers, in part, the same field, but is different enough from Peptide Chemistry, to justify publication of a revised edition of the latter. Princeton, July 1993 M. Bodanszky Preface to the First Edition Nature applied peptides for a great variety of specific functions. The specificity provided by the individual character of each amino acid is further ehanced by the combination of several amino acids into larger molecules. Peptides therefore can act as chemical messengers, neuro­ transmitters, as highly specific stimulators and inhibitors, regulating var­ ious life-processes. Entire classes of biologically active compounds, such as the opioid peptides or the gastrointestinal hormones emerged within short periods of time and it is unlikely that the rapid succession of discoveries of important new peptides would come to a sudden halt. In fact, our knowledge of the field is probably still in an early stage of development. Peptides also gained importance in our everyday life.