The purpose of this descriptive, qualitative study was to explore young adult women's conceptualizations of their menstruation experiences using a feminist approach. Grounded theory was used to understand how 15 college-aged women (ages 18-22 years, 86% white) evaluate their menstrual patterns as "normal" or "abnormal." Data analysis of the semi-structured interviews revealed four themes that the women used to judge the pattern of their menstruation (i.e., interval, duration, discomfort, and volume) as normal: (1) Pattern resembled learned norms, (2) consistent pattern discordant from learned norms, (3) predictably variable pattern, and (4) absence of problems. Two distinct themes informed their decisions to consider a menstrual pattern as abnormal: (1) Unpredictable variability, and (2) extreme experiences. The core variable emerging from data analysis, establishing a personal norm, illuminated the two major sources that women relied on in trying to interpret their menstrual patterns: the limited and often inaccurate information that they had been taught and their own menstrual experiences. Implications include the need to improve education about menstrual variability throughout the life cycle and about the diversity of women's normal menstrual patterns and experiences.