The population of England and Wales is becoming older. This poses an increasing demand for detailed data on the size an trends of the population at the oldes ages. Using the recently released Offic for National Statistics estimates of th population aged 90 and over in England and Wales, this article shows trends in the population of the oldest old and demographic causes of the rapid increase in centenarians during the twentieth century. It also presents further validation of the ON estimates of the oldest old with estimat from other data sources.