Terrorist and criminal acts must now be considered in the safety analysis of plants. The primary response of government and industry is improved security systems to prevent or thwart attacks. If a facility is attacked, the extent of the inflicted damage is determined by the available plant safety systems. A collaborative industry and academia case study for a new unit in a domestic U.S, refinery is undertaken to assess two issues: 1. What performance can be expected from conventional safety systems in response to a terrorist attack, if existing systems are not changed? 2. Can existing process hazards analysis methods be exploited or modified to address process threats? Evaluation of safety system performance is analyzed from two directions. The first involves a review of the deviation-driven process hazard analysis to gain insight into ways current methods can be leveraged to address process threats. The second approach is consequence-driven to analyze the performance of existing safety systems for catastrophic scenarios. The results of these two approaches lead to the following conclusions. 1. Current process hazards analysis techniques are robust for identifying hazards and safeguards, and managing risk. These practices can be extended to include additional scenarios related to intentional initiation of events. 2. Procedural layers of protection may not be reliable, if they can be intentionally ignored or compromised. 3. Facility layout and siting studies should not be limited to new facilities. For existing facilities, these studies may reveal opportunities to minimize risk of injury, environmental and property damage, and business interruptions. (C) 2004 American Institute of Chemical Engineers Process.