The first part of this paper examines future changes in the age structure of the population of England and Wales which are likely to occur as a result of past and future changes in fertility and mortality. These changes in fertility and mortality are examined in some detail. Different methods of projecting future changes in mortality are discussed. On the basis of conservative estimates of these changes, estimates are made of the future economic strain of dependency and there is some discussion of the way in which this might be best handled to the advantage of both the active and the elderly populations. The second part of the paper looks at different ways of examining improvements in longevity and also discusses some of the biological and environmental factors involved. Reference is made to the limited morbidity data available and the tentative conclusion is reached that improvement in longevity, so far, owes less to the reduction of disease incidence than to medical maintenance. This review paper, which relates to England and Wales, is in two main parts: (1) a general discussion of the population factors and changes which have led to a focusing of attention upon the ageing of the population and associated economic problems; and (2) a consideration of the implications of current health advances for individual survival.