A field experiment was conducted in a university library to assess the effect of symbolic territorial cues on preventing the theft of a photocopy card which was left on a library desk. Territoriality was conceived as comprising two dimensions - ownership and guardianship. In a 2 2 design, ownership was operationized by signing or not signing the card, and guardianship was operationized by leaving the card next to library books or on its own. Both territorial cues were successful in reducing theft levels. It was argued that the crime prevention role of territorial cues needs to be conceived of in terms that are broader than alerting potential offenders to increased levels of surveillance. (Published Abstract)