Drawing from oral history interviews, biographical accounts, and other sources of information on 60 women born between the 1920s and 1990s, this paper examines the changing history of young girls' experiences of menarche in Taiwan since World War II. Young girls who experienced their menarche before the 1970s were often caught by surprise and filled with fear about what was going on with their bodies. In contrast, as a result of menstruation education beginning in the 1970s, later young girls were much more likely to possess knowledge of menstruation long before its arrival. This paper pays special attention to generational differences in girls' level of knowledge about menstruation before it first occurred, where they were when they had their first period, if or when menstruation was a possible topic of conversation, and who was involved in caring for their menstruating bodies. From the 1970s, in addition to girls being educated in ＂correct＂ menstruation knowledge as a result of industrialization and nine-year compulsory education, girls increasingly experienced their menarche in a public setting, often with much embarrassment. Medical practitioners in Taiwan, including physicians, nurses, hygiene education professionals, and public health professionals, often working with sanitary napkin companies, began to advocate health education for school girls. Menstruation education- from institutional instruction to newspaper advice columns to popular health books- also profoundly changed the ways girls experienced their period, including the possibility of open conversation about the subject and involvement by males (e.g., fathers, brothers, and male peers). I argue that the ways in which different generations of women in Taiwan experienced their menarche were shaped by the politics of the communication of gendered knowledge within shifting structures of social relations.