Physicians have special professional obligations to respond to medical emergencies. A bioterrorism attack would be a medical emergency. Thus, it seems that physicians would have an obligation to respond to a bioterrorist attack. However, the scope of those obligations, and their limits, are vexed topics. General rules may be comforting but the details and nuances of particular situations will always be relevant.This work was supported by the MacLean Center for Clinical Medical Ethics. The funding source had no role in the analysis or in the decision to submit the manuscript for publication.