This article reports social inequalities in mortality in men aged 25-64 years in England and Wales, in the period 2001-03 using unlinked data sources and 2001-04 using linked data sources. It represents the first official analysis of premature mortality by the final version of the National Statistics Socio-economic Classification introduced in 2001, and updates the tradition of decennial reporting of mortality by socio-economic status. These results set a benchmark for inequalities in mortality in men of this age, providing insights into the impacts of different social and occupational circumstances in the early 21st Century and enabling future monitoring. The Office for National Statistics intends to extend this work to examine inequalities to mortality in females of the same age, in causes of death and by Government Office Region.