Since the fall of the Berlin Wall and the access to new archives previously kept secret by the Soviet Union, historians of Nazism have had a growing tendency to believe that the historical narrative should be based exclusively on archives and refrain from using eyewitness testimonies, which are such fragile sources. This article argues, on the basis of the case of Adolf Eichmann’s involvement in Zyklon B deliveries to the extermination camps, that such an approach is unsatisfactory. Without eyewitness testimonies, neither Eichmann’s implication in this activity (which he of course always denied) nor the role played by Kurt Gerstein could be narrated. Taking into account only what is documented in archives would, therefore, mean relinquishing the aim of creating as complete a picture of the past as possible. In the case discussed in the article, this would mean forfeiting information that can alter the usual perception of Eichmann, Gerstein, or the workings of the RSHA.