Background: Past research has determined that fear of violence is often "irrational" in relation to the actual level of risk presented. This has been found to exacerbate the negative effects of exposure to work-related violence. Aims: This study investigates fear of assault in relation to exposure to challenging behaviour. The extent to which a social psychological model of fear of assault can be generalised to care staff working with individuals with intellectual disability (ID) was tested and the validity of the instruments used was assessed. Method: A total of 87 care staff took part in a questionnaire-based study carried out in two separate and distinct organisations providing residential services to individuals with ID. In one service, staff exposure to challenging behaviour was high, with many clients having a forensic history, and in the other, staff exposure to challenging behaviour was low. Results: According to one measure, care staff exposed to high levels of challenging behaviour were more fearful about work-related violence. However, no difference was found between the groups on the second measure. Regression analyses indicated some support for the generalisability of dimensions of the model of fear of assault in explaining feelings of unsafety. Conclusions: This study suggests that fear of assault may be an important factor when trying to understand care staff responses to challenging behaviour. However, the equivocal nature of the results raises questions about the validity of existing methods of assessing this fear. (Contains 5 tables.)