This article, based on a report (Women, aging and health: achieving health across the life span) prepared for the WHO Global Commission on Women's Health under the guidance of WHO's Aging and Health Programme, presents demographic data that clearly demonstrate the need for recognition of the health of aging women as a global issue of major public health concern. The authors show that, while female life expectancy at birth is significantly different in developed and developing countries (because of high infant and maternal mortality in the latter), these differences tend to decrease for women in developing countries who reach middle age. The authors review the various facets of the "gender transition" brought about by demographic and epidemiological transitions, drawing attention to contrasts between the situation in developing countries in Asia and Latin America and that in Eastern Europe, for example. The role of older women as care-givers is discussed, as is the likelihood of a future increase in the proportion of older women living alone in the developing world (a factor which renders them particularly vulnerable in many socioeconomic and health respects). Suggestions are made on methodologies for monitoring health trends in aging women, and on the role of WHO in this respect. A basic goal for global strategies relating to the health of older women is formulated: reduction of the inequities in life expectancy between developed and developing countries.