CONTEXT: The Stages of Reproductive Aging Workshop proposed bleeding and hormonal criteria for the menopausal transition, but operational definitions of hormone parameters were not specified. OBJECTIVE: This paper investigates the longitudinal relationship of annual serum FSH levels with four proposed bleeding criteria for the late menopausal transition in two cohort studies. The goal is to provide empirically based guidance regarding application of hormonal criteria that may be optimal for widespread application in clinical and research settings for assessing menopausal stage. DESIGN/SETTING: Prospective menstrual calendar and annual serum FSH data were collected from two population-based cohort studies: the Melbourne Women's Midlife Health Project and the Study of Women's Health Across the Nation. PARTICIPANTS: Participants in the study were 193 Melbourne Women's Midlife Health Project and 2223 Study of Women's Health Across the Nation women aged 42-57 yr at baseline who contributed 10 or more menstrual cycles and at least one annual serum FSH value. MAIN OUTCOME MEASURE(S): Association between bleeding criteria for the late menopausal transition and FSH was a main outcome measure. Associations of bleeding criteria, FSH, and hot flashes with the final menstrual period were also measured. RESULTS: A single FSH measure is an independent marker of the late menopausal transition, but FSH concentrations are less predictive of menopausal stage than any of four proposed bleeding criteria. Criterion FSH values for the late transition are similar across both studies. Experience of hot flashes adds no information in the presence of hormonal and bleeding criteria. CONCLUSIONS: An annual serum FSH concentration of 40 IU/liter could be incorporated, in conjunction with bleeding markers, into the Stages of Reproductive Aging Workshop paradigm for markers of the late menopausal transition.