The provision of mechanical ventilatory support for large numbers of casualties in disasters is a complex, controversial issue. Some experts consider this modality unsuitable for large disasters and a waste of resources better devoted to eminently salvageable victims. However, the reality has usually been that rescue teams bring with them some ventilatory capability, even if only for perioperative support. Also, there are many instances when the environment, the existing and potential capacities, allow for significant numbers of victims to be saved by providing artificial ventilation, that would otherwise have likely died. It is therefore important to discuss the issue, with all its complexity, so that the disaster preparedness and relief community fully understands its implications and makes informed, locally relevant decisions before and after disasters strike. The purpose of this presentation is to describe the ethical dilemmas, the technical and clinical considerations for such an endeavor. Ethical considerations: providing the most care to the most victims is the dictum of disaster medical management. Lowered standards of care are accepted and often the norm. However, in many moderate and even major disasters, the ability exists to save lives that will certainly be lost otherwise, by providing intensive care including mechanical ventilatory support, or may be provided if the managers so determine. Is it then ethical, to allow certain victims to die when such support may be available? What is the cost-benefit ratio of such a decision? Who should receive this limited resource? The young and healthy? The very sick? The salvageable? The postoperative? For how long? Until the international team leaves? Types of ventilator-dependency in disasters: (1) Primary ventilatory failure, normal lungs, prolonged ventilator dependency, e.g. botulinum toxin; (2) Combined ventilatory and hypoxemic failure, short to medium-term ventilator dependency, e.g. Sarin gas intoxication; (3) Primary hypoxemic failure, parenchymal lung injury, prolonged ventilator dependency, e.g. Anthrax, mustard gas, ricin; (4) Perioperative and prophylactic ventilatory support, short term but unpredictable. Ventilator supply versus demand: (1) Insufficient ventilators for first few hours only, then supplies come in; (2) Insufficient ventilators for days, then national or international relief expected; (3) Insufficient ventilators and no expected supplies. Care environment: (1) ICU, minority of casualties; (2) General floors: inexperienced nursing, medical staff; (3) Insufficient monitoring devices; (4) Insufficient numbers and quality of respiratory therapists; (5) Commercial companies normally providing technical support understaffed. Basic requirements from the ventilators: allows spontaneous ventilation, incorporates some alarms (ideally disconnect and minute volume), made by a reputable and stable company (will be there when the disaster strikes), low cost, user friendly, long shelf life, quick activation from storage, low weight and volume, few spares, few or generic disposables, little and simple maintenance, independent of compressed oxygen (i.e. electric, multiple voltages, long-life battery). The system: Mechanical ventilation is a complete patient care unit comprising: Bed and space, Oxygen supply, Vacuum, Cardiorespiratory monitor, Mechanical ventilator, Nursing staff, Medical staff, Expert consultatory staff, Logistic and technical support staff. Potential mechanical ventilators: (1) BVM or bag-valve-tube; (2) Transport-type, pneumatic or electrical ventilators; (3) Intermediate capability pneumatic, electrical or electronic ventilators; (4) Full capability intensive care ventilators; (5) Single patient use ventilators.