This paper presents a methodology for the assessment of the performance of industrial hazardous materials emergency plans. This approach is based on a structuro-functional model of the emergency plan, which highlights the plan's functions, resources, support services and interactions. A resource taxonomy is used to manage the complexity of the emergency response system. The model can be used both as a planning guide and for the analysis of the performance of the emergency response system, based on the risk assessment of the system. The failure probability is estimated through the plan's functions and resources fault trees. The failure severity of each function is determined by using the facility's hazard study. The failure criticality of each function is hence obtained.