The use of qualitative interviews within the evaluation researchThe last trends in evaluation consider the necessity to carry out on participatory evaluation focused on the change theories. There have been different authors with diverse interpretations in relation to the role from the theory into the evaluations. These approaches are: the theory-driven evaluation elaborated by Chen and Rossi (1990), theory-based evaluation by Carol Weiss (1995) and the realistic evaluation formulated by Pawson and Tilley (1997).All these theories try to respond to the question on how to link the different effects from the programs with their causes. What it is known as "the Black Box problem" (Stame, 2002). Each one of this approaches interpret the problem in a different way. For Chen and Rossi, the problem of the black box is interpreted affirming that there is no theory, since the goals of the programs are not clear and they are not adequately defined. For Carol Weiss, the programs have many theories that take the form of tacit knowledge that would have to be made explicit. Weiss distinguishes within the change theories two components: theory of the implementation and the programmatic theory. Therefore the role of the evaluations based on the theory is to clarify these mechanisms, to divide to the program in the subsequent mechanisms and to use all kind of data to verify them. In this way, the approach helps to generate new theories.The last approach "realistic evaluation" whose precursors are Pawson and Tilley, is based on a genetic theory of the causality, considering that the changes are no produced by the program but by people exposed to the programs. People activate some mechanisms that produce the change.This is our conceptual framework. Our purpose is to know the change theories that have the participants on a program. The objective of this paper is to discuss the use of the qualitative interviews as an instrument that facilitates the construction of knowledge on the program on the hand of the participants. For this reason, we discuss the following aspects taking as focus a higher education teacher training program developed at University of Cadiz and managed by the UCUA (Unit for the Quality of the Andalusia Universities):v A framework to build a theory of programs. The use of qualitative approaches. Relations between the theory and the practice in the field of the evaluation. v Theories of the change in evaluationv The interview as an instrument for the generation of knowledge within a program. In depth interview in the case of a higher education teacher training program v Types of interviews and their relation with the task of constructing knowledgev The validity in the research processes with interviews: communities of validation and contexts of interpretation.