As tariffs on imports of manufactures have been reduced as a result of multi-lateral trade negotiations, interest in the extent to which existing nontariff barriers may distort and restrict international trade is growing. Accurate and reliable measures are needed in order to address the issues involving the use and impacts of nontariff barriers. This study assesses currently available methods for quantifying such barriers and makes recommendations as to those methods that can be most effectively employed. The authors focus both on the conceptual issues arising in the measurement of the different types of nontariff barriers and on the applied research that has been carried out in studies prepared by country members of the OECD Pilot Group and others seeking to quantify the barriers. Nontariff barriers include quotas, variable levies, voluntary export restraints, government procurement regulations, domestic subsidies, and antidumping and countervailing duty measures....