Although the purpose and scope of this monograph remain unchanged, I have been obliged to revise and rewrite many sections to keep pace with the recent growth in knowledge of endometrial pathology and physiology. New knowledge emanates from every quarter, engendered by improved meth ods of study in virtually every subspecialty, by exemplary cooperation between disciplines, and especially by the exchange of ideas internationally. On the other hand, the catalogue of diseases is everchanging. Some, once common, become rare or even disappear. Others suddenly appear, unique and previously unknown. Increased longevity, modern ways of living and new methods of treat ment have modified or augmented the clinical and diagnostic problems confront ing us. Accordingly, therapy with hormones and intrauterine contraception re ceive special attention, commensurate with the importance afforded them today. Under the precept "nil nocere," the almost unlimited uses for these agents warrant that their effects be carefully monitored by precise morphological stud ies, a prerequisite that succeeds only when clinician and pathologist cooperate closely. The sections on procedures for obtaining endometrial tissue, on steroid receptors, on functional disturbances, and on spontaneous abortion have been changed or expanded to incorporate new facts from recent discoveries that now appear significant. Only time, however, will prove their true value. Much of historical interest in the text has been left intact, for "who wants to read into the future, must consult the past" (Andre Malraux).