From 9/11 to SARS to Hurricane Katrina, public health emergencies and mass casualties catch us off guard and overmatched. How can medicine prepare to respond to the next emergency rather than to the last one? To answer that question medicine must resolve the many ethical concerns embedded in methods for preventing and containing disease, some of which restrict civil rights; the design of triage protocols for treating the injured; and protections for physicians who participate in relief efforts. This month’s authors think much work remains to be done.