This monograph has been written in the hope that it will prove of value to medical students and clinicians, to Honours undergradu ates in appropriate branches of the natural sciences, and to repro ductive biologists in general. It would be pleasing if the text also caught the attention of veterinary undergraduates, since there is much information bearing on reproduction in domestic animals. First and foremost, however, the intended audience is a medical one, for scientific studies of human reproduction have been cata lyzed by the intense interest in procedures of fertilization in vitro. Some would judge that this very activity has narrowed our view of physiological events occurring within the Fallopian tubes. The pre sent work may therefore serve as a useful counterbalance to the overwhelming series of publications on procedures of in vitro fer tilization, and offer opportunities to those in the clinical field for extending their knowledge of the scientific background to much of the current work.