Capacity development is a fashionable notion as well as a popular activity, on which governments and international agencies spend much time and effort. However, these activities have not always led to the expected impact: while improving individual skills, they have seldom succeeded in transforming the organizations to which these individuals belong, including ministries of education. Against this background, IIEP/UNESCO undertook a wide range of studies to examine the reasons for this relative failure and to propose innovative and relevant policies and strategies. The conclusions are that capacity development is a very complex endeavour: the constraints are not related simply to lack of skills but to a wider and intricate web of factors, constituted for instance of ineffective use of staff, counterproductive incentives, absence of leadership and weakness of internal and external monitoring systems. Training as an isolated intervention does not have much impact, because it fails to change bureaucratic cultures. Capacity development demands that more attention be given to organizational development and change. This synthesis paper ends with an overview of strategies which international organizations can implement and with a set of principles which can guide all actors.