This article describes a system dynamics analysis of the 1992 Westray mine disaster in Nova Scotia, Canada. It examines the causal structure of the Westray system, including relationships that could have led to conditions that caused the fatal explosion at the mine. The value of simulation is its ability to capture a “mental model” of the safety system, which can stimulate discussion among safety experts as to the systemic causes of a disaster. By taking into account feedback loops and non-linear relationships, which is not possible with conventional root-cause analysis, a dynamic model of the system provides insights into the complex web of causes that can lead to disaster and valuable lessons for organizational learning. Copyright © 2003 John Wiley & Sons, Ltd.