Menopause signifies the permanent cessation of ovarian function and the end of a woman's reproductive potential. A universal experience in women's aging, it is the culmination of some 50 years of reproductive aging--a process that unfolds as a continuum from birth through ovarian senescence to the menopausal transition and the postmenopause. The menopausal transition is known to play a major role in the etiology of many symptoms common in middle age and may contribute to chronic conditions and disorders of aging such as osteoporosis and cardiovascular diseases. However, the mechanisms underlying ovarian senescence and the occurrence of various short- and long-term biological and psychological sequelae are poorly understood. Progress in researching reproductive aging and the menopause has been impeded by the lack of a staging system based on meaningful, reliable, and objective criteria for staging reproductive aging and specifying menopause-related status. Current nomenclature is described and its limitations are discussed. Specifically, contemporary terminology lacks the sensitivity and specificity needed to operationally define a woman's reproductive status in the continuum of reproductive aging. A number of proposed staging systems are currently being evaluated for their suitability in identifying appropriate demarcations across the span of reproductive aging. Further research and a better understanding of the menopausal transition are necessary to establish the validity, practicality, and acceptability of these proposed staging systems.