We argue that in seeking to insure against model uncertainty, monetary policy makers are often ready to trade ex post performance for greater certainty in the outcome. They thus look for rules that although not optimal ex post, have certain properties that qualify them as robust. We apply first, Gul's approach of ‘disappointment’ aversion to describe policy makers' aversion to uncertainty and then define the properties the notion of ‘robustness’ entails. With these two tools we then link the desirability of such robust rules to the degree of policy makers' aversion to uncertainty. We thus show that provided such robust rules exist, a larger degree of disappointment aversion leads to a greater emphasis on robustness in policy implementation.