This chapter deals with the question of methods in defence studies. Social science research on defence and the military has grown increasingly in international academic research in the last decades. As the military constitutes a specific social institution, researching defence and the military is not only pertinent but also indispensable because the use of violence has become an important characteristic of the post-Cold War conflicts. And yet though very numerous publications on defence questions exist, still few of them are dedicated to methodological questions. In this chapter we postulate the specificity of defence as a social field. Thus it is important for the social scientists to be aware of this specificity and cope with it. The chapter first analyses the four main debates about methods in defence studies: the insider/outsider dilemma, the choice for quantitative or qualitative studies, the question raised by the use of interviews in defence studies and the question of secrecy. Then in a second part we illustrate the question of the use of qualitative interviews in defence studies by a case study. In a third part, the chapter raises the question of new technologies and social networks in defence studies. Finally, the chapter concludes with the importance of reflexivity in investigating the defence field.