The dissertation makes a contribution to the history of contraception by showing the interplay of scientific, religious, public administrative, and other groups in the development and dissemination of natural birth control.. The project will examine in particular the process whereby the current notion of the woman's time of evaluation was established and applied to the development of birth control methods, especially rhythm methods. This study will, for the first time, trace the steps of the process that led from work done in European, Japanese, and American laboratories to its social impact. It will take into account the interplay of the various agents involved (researchers, medical practitioners, government, and religious authorities), showing how their different values (professional, moral, religious, and ideological) have interacted. Further, the research takes up religious differences as they are reflected in national differences, between a Roman Catholic dominated state and one where separation of church and state is rhetorically important but does not describe politics as practiced.