[Evaluation of epidemiologic surveillance systems: analysis of different approaches in a study in Ecuador]

Based on the experience of the assessment of public health surveillance systems, this paper explores the relationship between knowledge and action. Like research, evaluation is a cognitive process however oriented to a specific aim. Thus it is possible to compare the various approaches of evaluating these systems using the frame of paradigms in sciences (positivism, post positivism, critical theory and constructivism). In addition, evaluation aims to improve the functioning of the system, to introduce changes in it. The fourth generation evaluation, as it has been done in Ecuador, is an interesting way of acquiring understanding of the system while solving its malfunctionings. In this experience, the evaluator seeks the participation of the actors of the system at each steps of the evaluation process. He searches to involved them through three levels: intellectual, affective and ontological.