Abstract There is a fundamental incompatibility between ef?ciency, interim individual rationality, and budgetbalance in mechanism design, even for extremely simple settings. Yet it is possible to specify ef?cient mechanisms that satisfy participation and budgetbalance constraints in expectation, prior to types being realized. We do so here, in fact deriving mechanisms that are individually rational for each agent even ex post of other agents’ type realizations. However, participation must still bear some risk of loss. For agents that are risk neutral, we show how the center can extract the entire surplus in expectation, or alternatively provide an equal expected share of the surplus for each participant, without violating dominant strategy incentive compatibility, ef?ciency, or ex ante budget-balance. We compare these solutions to a third ef?cient mechanism we design explicitly to address risk aversion in trade settings: payments are de?ned to minimize the odds of loss, satisfying ex ante participation constraints for agents with attitudes toward risk ranging from neutrality to high loss-aversion.