Classical economists engaged in a vigorous debate over whether Britain's tariff reductions in the 1840s should be made contingent on tariff liberalization abroad. Some, notably Robert Torrens, believed that a unilateral tariff reduction would so deteriorate British terms of trade as to outweigh efficiency gains and make the country worse off. In this paper, Britain's foreign trade elasticities are estimated for this period in a simultaneous equation model. They are used in a simple general equilibrium model that explicitly takes the terms of trade into account to assess the welfare impact of tariff reductions. The results indicate that Britain would have been made worse off from a unilateral tariff reduction. However, foreign tariff reductions mitigated the terms of trade deterioration and could easily have made Britain better off. Copyright 1988 by University of Chicago Press.