This paper examines the impact of one leadership development programme, drawing on a model developed by Leithwood and Levin (2004) for the Department of Education and Skills. The New Visions programme, offered by the National College for School Leadership, is aimed at new headteachers and adopts a process rich approach to leadership development. The paper uses evidence from the authors' evaluation to show that the programme had a significant impact on participants' knowledge and skills, and on their leadership practices, but a more limited effect on classroom practice and pupil outcomes. (Contains 2 figures.)