A broad range of factors have been identified as having an impact on burnout and performance. To improve our understanding of how these factors interact, a model of carer stress is tested. Staff were surveyed in residential units, assessments included burnout, organizational factors, staff cognitions and ratings of resident challenging behavior. The relationship between challenging behavior and emotional exhaustion was fully mediated by fear of assault. The relationship between emotional exhaustion and experienced safety (an organizational variable) was also fully mediated by fear of assault. The use of the model with staff is supported and it suggests that staff burnout can be reduced by influencing either staff cognitions, organizational factors or challenging behavior or a combination of these factors. (Contains 7 tables and 2 figures.)