A comprehensive review of the yeast cell envelope has not appeared previously and therefore this book is timely. The title of this volume was chosen to reflect the three major areas of contribution to our current understanding of the cell envelope, but we have not attempted to group chapters into subdivisions. The approach was to describe phenomena, to review the literature and to illuminate outstanding problems. It was also attempted to generate working hypotheses which may stimulate further studies. The some of these ideas be of germinal value is of more concern to us than that all of the hypotheses should stand the test of further experimentation.