This article seeks to clarify the terminology and methods of planning to avert hospital internal disaster. It differentiates “crisis” from “disaster” in the in-hospital setting. Preparedness, as contrasted with mitigation, is meant to reduce the likelihood that a crisis will turn into a disaster. Though there are some recurring features of crises, allowing for preparedness through the identification of a few high-likelihood contingencies, crises are subject to numerous, overwhelming uncertainties. These include hazard uncertainty, incident uncertainty, sequential uncertainty, informational uncertainty, consequential uncertainty, cascade uncertainty, organizational uncertainty, and background uncertainty. In view of the uncertainties, the primary aim of planners should not be to try to create plans for ever more contingencies, since contingencies are far too numerous and perhapsapproach infinity, but rather to create capabilities (through proper preparedness) for resilience during crisis. Resilience can be cultivated through improvements in information acquisition and dissemination, communication systems, resource management, mobility management, design for resilience, incident command, and staff versatility.