This essay reviews and defines avoidable medical error, malpractice and complication. The relevant ethical principles pertaining to unanticipated medical outcomes are identified. In light of these principles I critically review the moral culpability of the agents in each circumstance and the resulting obligations to patients, their families, and the health care system in general. While I touch on some legal implications, a full discussion of legal obligations and liability issues is beyond the scope of this paper.