Recent decades have seen a significant increase in physicians participating in international short-term missions to regions with limited or no access to health care by virtue of natural disaster or lack of resources. Recent publications in the ethics literature have explored the potential of these missions for unintentional harm to the intended beneficiaries. Less has been discussed about how to respond when harm actually occurs. The authors review the ethical issues raised by short-term medical and humanitarian missions and the literature (...) on responding to unintended error to provide guidelines for avoiding harm to the intended beneficiaries of missions and an appropriate response when harm occurs. Two cases demonstrating an analysis and response to unintended harm are presented. (shrink)