School leaders have been given an important role in initiating and implementing school improvement, which demands new forms of leadership. This invokes the question of the basic competences for leadership that are presently required. This article focuses on the formulation of competences for school leaders in the Netherlands with the aim of supporting them in their personal and team development. The school leaders' union for secondary education in the Netherlands set up a working group of academics, consultants and school leaders to define these competences. Taking the research evidence of effective leadership as point of departure, the working group formulated a set of five general basic competences. The competences were placed in a general model of effective leadership. An action plan was developed as a tool for individual school leaders and leadership teams to translate the five core competences into context-specific competences for their own school. (Contains 2 figures and 2 notes.)