In a crisis situation, critical success factors include good preparedness, the availability of trustworthy information and reliable people, and the responders' ability to improvise with the available, functioning tools. Wikis can be used as collaborative group support systems to support these activities, especially for communities of practice that must operate as high reliability organizations. The advantages of using a wiki are especially beneficial in volatile environments, such as those in the emergency domain, where critical real-time decision making is required. An international wiki - emergenciWiki.org - has been created and is being used by both practitioners and academics. The conclusions include that wiki features and functionality, which are important for safety- critical work, should add a minimum of bureaucratic overhead while helping to establish trust and a sense of purpose and community among the users, thus easing the evaluation of information reliability while strenghening ad hoc group interaction.