Greater Boston and Massachusetts were used as prototypes to evaluate the feasibility of, and requirements for, reopening a shuttered hospital to expand surge capacity during an urban mass casualty event. Massachusetts health planners previously identified the need for 150-250 additional beds for a surge event; this is the scale of operation explored in this project. Other communities may be considering this option as well. Our objective was to develop tools to help planners determine whether this option is feasible in their local communities and to carry out the advance planning and preparation that would be required. After considering several candidate facilities, conducting careful walk-throughs and assessments of two candidate facilities, and discussing options with the owners of several others in the greater Boston area, we concluded that the following factors would help emergency planners evaluate candidate shuttered hospitals and determine the most likely candidates for surge capacity expansion: A completely abandoned hospital that has been vacant for many years would likely have been stripped of anything saleable and will no longer have working utilities, fire and life safety systems, or even possibly water and sanitation fixtures. Thus a totally shuttered facility cannot safely be converted to inpatient care in a timely manner; Location and the relative local value of the real estate involved may indicate the likelihood that a facility will remain empty and available or be converted to other purposes such as condominiums or assisted living; Similarly, a shuttered hospital may have an uncertain ownership status, may be owned by a city or a developer, or may be part of a bankruptcy proceeding. Uncertain or changing ownership may mean that no one is legally able to negotiate for the use of the facility in an emergency. A partially-shuttered hospital that maintains some sort of affiliation with a tertiary hospital (e.g. urgent care center, walk-in clinic) may be a more likely candidate for surge capacity since organizational/contractual arrangements already exist that can be used to advantage in an emergency; A larger shuttered hospital may have more to offer than a very small one for surge capacity purposes; A surge facility located fairly close to the major tertiary medical centers may be advisable to minimize patient transportation time and issues; A facility that maintains a cafeteria and food preparation area, certified life safety systems, a phone switch, and similar basic functionality would be better than one that is entirely vacant and unused. Planners could rank potential surge facilities using a list such as this, as a first step in identifying the best candidate facilities. The resulting list of candidate facilities should be reassessed periodically, as the status of facilities can change over time.