The use of secret police archives by researchers to trace the history of repression and collaboration and to understand the methods employed by totalitarian regimes to control their populations is well established. The significance of these archives for the study of material religion, however, has been largely overlooked by scholars. The Secret Police archives in Romania and Moldova constitute a hidden repository of confiscated religious art, materials and publications that in many cases survive nowhere else, presenting an exceptionally rich resource for the study of religions in the 20th century. These archives, therefore, represent an important resource for understanding how religious groups deployed various creative art and media in resisting and critiquing the totalitarian and authoritarian system of the time. They also present us with “authoritative” accounts of belief systems and worldviews judged to have been dangerous and subversive and tantalising glimpses of religious lives lived during rapid social and political transformation. The ideological nature of the archives and the oppressive practices they represent, however, present the researcher with distinct challenges in terms of methodology and ethical practice. In this paper, I will outline some of the challenges of interpretation of archival data on religious belief and practice as well as some opportunities presented by this rich resource of religious “ephemera” captured in secret police agents’ and informers’ reports, photographs and confiscated materials.