Sir Richard Doll, FRS, FRCP ICRF Cancer Research Studies Unit Radcliffe Infirmary, Oxford, UK The twentieth century has seen few changes more remarkable than the improvement in health that has occurred nearly everywhere, most spectacularly in the economically developed countries. In these countries improved nutrition, better housing, the control ofinfection, smaller family sizes, and higher standards of education have brought about a situation in which more than 97% of all liveborn children can expect to survive the first half ofthe three score years and ten that formerly was regarded as the...