This analysis of mortality in old age in 28 countries is based on 386 million person-years of observation of which 52 million ended in death. Of these, 122,000 were deaths at ages 100 and over. The recent extraordinary decline in mortality in old age has spread to virtually all developed countries but its onset and magnitude have varied widely from one country to another and the rates show no tendency for convergence. The development displays nevertheless many features common to all. The book concludes with estimates of the effects a continuing mortality decline would have.