CONTEXT: The current criterion for onset of late menopausal transition is amenorrhea of 90 d or more. The Stages of Reproductive Aging Workshop proposed alternative criteria based on a shorter period of amenorrhea. Empirical data comparing proposed criteria are not available. OBJECTIVE: This paper evaluates the several bleeding criteria that served as the basis of these recommendations. The goal was to provide empirically based guidance regarding which bleeding criterion may be optimal for widespread application in clinical and research settings. DESIGN/SETTING: The study used prospective menstrual calendar data from four community and population-based cohort studies: TREMIN, Melbourne Women's Midlife Health Project, Seattle Midlife Women's Health Study, and Study of Women's Health Across the Nation. PARTICIPANTS: The study included 735 TREMIN, 279 Seattle Midlife Women's Health Study, 216 Melbourne Women's Midlife Health Project, and 2270 Study of Women's Health Across the Nation women aged 35-57 yr at baseline who contributed 10 menstrual cycles or more. MAIN OUTCOME MEASURE(S): The main measures were the frequency of and median age at occurrence and time from occurrence to final menstrual period (FMP) for four criteria: skipped segment, 10-segment running range, 60- and 90-d amenorrhea. RESULTS: A skipped segment, 10-segment running range greater than 42 d and 60-d amenorrhea identify a similar time in women's reproductive lives. The latter two identify the exact same date in two thirds of women. All three criteria occur in a greater proportion of women than the 90-d criterion and are equally predictive of the FMP, although they occur 1-2 yr earlier. CONCLUSIONS: These findings support the recommendation of the Stages of Reproductive Aging Workshop that 60 d of amenorrhea be used to define onset of the late menopausal transition.