In this paper, the authors examine the economic consequences of existing U.S. restrictions on trade in domestic water transportation (cabotage) services. They briefly trace the history of U.S. policy on cabotage. The authors also use an applied general equilibrium model of the United States to analyze the effects of the Jones Act on welfare and on production, trade, and employment in important upstream and downstream sectors. The economic effects of U.S. maritime policies rank them with U.S. trade policies like the MFA, the automobile and steel quotas of the mid-1980s, and agricultural import restraints. Coauthors are Hugh M. Arce, Kenneth A. Reinert, and Joseph E. Flynn.