The current thesis explores conditions for participation in interview interaction. Drawing on the ethnomethodological idea that knowledge is central to participation in social situations, it examines how interview participants navigate knowledge and competence claims and the institutional and moral implications of these claims. The data consists of, in total, 97 audio-recorded interviews conducted as part of a national Swedish evaluation of support interventions for children exposed to violence. In three studies, I use discursive psychology and conversation analysis to explicate how interview participants in interaction (1) contribute to and negotiate institutional constraints and (2) manage rights and responsibilities related to knowledge.The findings of study I and study II show that child interviewees actively cooperate with as well as resist the constraints of interview questions. However, the children’s opportunities for participation in this institutional context are limited by two factors: (1) recordability; that is, the focus on generating recordable responses and (2) problematic assumptions underpinning questions and the interpretation of interview answers. Apart from restricting children’s rights to formulate their experiences, these factors can lead interviewers to miss opportunities to gain important information. Also related to institutional constraints, study III shows how the ideal of model consistency is prioritized over service-user participation. Thus, the three studies show how different practices relevant to institutional agendas may hinder participation.Moreover, the findings contribute to an understanding of how issues of knowledge are managed in the interviews. Study II suggests the importance of the concept of believability to refer to people’s rights and responsibilities to draw conclusions about others’ thoughts. And the findings of study III demonstrate how, in evaluation interviews with social workers, children’s access to their own thoughts and feelings are based on a notion of predetermined participation; that is, constructed as contingent on wanting what the institutional setting offers. Thus, child service users’ low epistemic status, compared to the social workers, trumps their epistemic access to their own minds. These conclusions, about recordability, believability, and predetermined participation, are based on interaction with or about children. However, I argue that the findings relate to interviewees and service users in general. By demonstrating the structuring power of interactive practices, the thesis extends our understanding of conditions for participation in the institutional setting of social research interviews.