Abstract. In general, diagrams and text are both considered to have their advantages and disadvantages for the representation of use case models, but this is rarely investigated experimentally. This paper describes a controlled experiment where we compare safety hazard identification by means of misuse cases based on use case diagrams and textual use cases. The experiment participants found use case diagrams and textual use cases equally easy to use. In most cases those who used textual use cases were able to identify more failure modes or threats. The main reason for this seems to be that use cases encourage analysts to specifically focus on threats related to the functions mentioned in the use case, and textual use cases include more functional details than diagrams. The focus is decided by information in each use case which will thus decide the number of threats identified.