Does inequality affect a group’s cohesion and ability to prosper? Participants in laboratory economies played an indefinite sequence of helping games in random, anonymous pairs. A coin flip determined donor and recipient roles in each pair. This random shock ensured equality of opportunity but not of results, because earnings depended on realized shocks. We manipulated the ability to condition choices on this uncontrollable inequality source. In all treatments, uncertain ending supports multiple Pareto-ranked equilibria, including full cooperation. Theoretically, inequalities do not alter the incentives’ structure. Empirically, inequality disclosures altered conduct, weakened norms of mutual support and reduced efficiency