Mechanical ventilation in a situation of mass casualty respiratory failure will require a substantial increase in the capacity for mechanical ventilation, to prevent unnecessary mortality. Concern over the difficulties of treating large numbers of patients with respiratory failure is exceeded only by our lack of experience on which to base decisions. This review evaluates the likely scenarios that could lead to mass casualty respiratory failure and the types of respiratory failure anticipated. A literature review was conducted, using the National Library of Medicine Medical Subject Headings terms "mass casualty respiratory failure," "pandemic flu," "disaster preparedness," and "mass casualty care." Papers were reviewed for relevance to the topic. There is little historical or empirical evidence upon which to base decisions regarding mass casualty respiratory failure and augmenting positive-pressure ventilation capacity. Matching the degree of respiratory impairment anticipated from the most likely mass casualty scenarios allows conclusions to be drawn regarding the performance characteristics of ventilators required for these situations. Little is known about the success of mechanical-ventilator stockpiling for mass casualty respiratory failure. Careful planning with an emphasis on matching ventilator performance to patient need and caregiver skill is critical to appropriate stockpile choices.