Since devolution in the UK in 1999, many aspects of social policy in Wales have been developed to respond more distinctively to the needs and requirements of those who live and work in Wales. In education and life-long learning, the Welsh Assembly Government has set out intended policy developments for the first ten years of devolved government in a paving document, "The Learning Country--a comprehensive education and lifelong learning programme to 1010 in Wales" (NAfW 2001a). These policies, if implemented, will mean that schools in Wales and the task of leading them will become increasingly different from other parts of the UK. This increasing distinctiveness has implications for the way aspiring headteachers are prepared for headship. In Wales, aspiring headteachers become qualified for headship through the National Professional Qualification for Headship (NPQH). The purpose of this article is to explore the NPQH in Wales and to raise issues for policy and practice in the development of educational leaders. These issues are likely to be significant for countries beyond the UK. The aim is to describe the development of NPQH in Wales, to analyse the nature of candidates' progress through the qualification, and to explore some key issues in the development of the headteacher profession in Wales. Following this introduction, there is a section that gives the background to the qualification, a section that explores candidate progress--the route through the qualification, and then a section that explores a number of significant issues for policy and practice. (Contains 1 table and 2 figures.) [For Part II, see EJ807061.]