We present a theory of honor violence as a form of costly signaling. Two types of honor violence are identified: revenge and purification. Both types are amenable to a signaling analysis whereby the violent behavior is a signal that can be used by out-groups to draw inferences about the nature of the signaling group, thereby helping to solve perennial problems of social cooperation: deterrence and assurance. The analysis shows that apparently gratuitous acts of violence can be part of a system (...) of norms that are Pareto superior to alternatives without such signals. For societies that lack mechanisms of governance to deter aggression or to enforce contracts, norms of honor can be a rational means of achieving these functions. The theory also suggests that cultures can become trapped in inefficient equilibria owing to path-dependent phenomena. In other words, costly signals of honor may continue to be sent even when they are no longer providing useful information. (shrink)