Failure to successfully communicate maintenance activities, abnormal conditions, emergency response procedures, process hazards, and hundreds of other items of critical information can lead to disaster, regardless of the thoroughness of the process safety management system. Therefore, a well-functioning process safety program depends on maintaining successful communication interfaces between each involved employee or stakeholder and the many other employees or stakeholders that person must interact with. The authors discuss a process to identify the critical "Interfaces" between the many participants in a process safety management system, and then to establish a protocol for each critical interface. (C) 2005 Elsevier B.V. All rights reserved.