Although many efforts have focused on studying methods to prevent incidents in major hazard plants, mishaps still occur because of various technical and human failures and random natural events. It seems that unexpected disturbances not being absorbed by the system and leading to catastrophes are unavoidable even under good risk management: this seems to be true especially today with the more complex systems. Resilience, which is the ability to recover quickly after an upset, has been recognized as an important characteristic of a complex organization handling hazardous technical operations. In response to the need to further improve the safety of industrial processes or plants, there is a need to study the resilience of a process operation incase unexpected events occur. The aim of this work is to propose the principles and factors that contribute to the resilience of a process. Both are identified based on literature reviews and expert opinions. Six principles, including Flexibility, Controllability, Early Detection, Minimization of Failure, Limitation of Effects, Administrative Controls/Procedures, and five main contributing factors, including Design, Detection Potential, Emergency Response Plan, Human Factor, and Safety Management are identified in this work. An example has been used to demonstrate and support recognized contributing factors. These principles and contributing factors can be applied to evaluations of the resilience of a design or process operation. (C) 2011 Elsevier Ltd. All rights reserved.