Part of the Aurel Stein Archives and Collections Conference: One of the main theories related to the reasons for the sealing of the Dunhuang library cave is that the manuscripts and paintings deposited there formed “sacred waste,” that is, religious artefacts that could not be destroyed even after they ceased to hold practical value. This explanation was advanced by M. Aurel Stein during his first visit to the Mogao Caves and was largely based on his observation that the materials included large bundles filled with manuscript fragments. A few months later, Paul Pelliot, following his visit to the library cave, advanced the theory that it had been sealed to preserve the Buddhist library from the invading Tangut forces. This paper proposes to examine Stein’s idea of sacred waste in light of the discovery of the Genizah depository only a few years prior to Stein’s expedition. My argument is that in explaining the nature of the library cave and the reason for its sealing, Stein was likely influenced by the Genizah finds and the contemporary discourse surrounding those.