This paper surveys the measurement of trade costs, both direct and indirect, and discusses the challenges and recent developments in understanding these costs. Trade costs are significant and vary widely across countries and goods. Direct measures of trade costs, such as tariffs and non-tariff barriers, are limited and often incomplete. Indirect measures, based on trade flows and prices, provide valuable insights but are subject to inference issues. The paper highlights the importance of theoretical frameworks in interpreting and improving the measurement of trade costs. It also emphasizes the role of infrastructure, policy, and economic geography in shaping trade costs. The authors present new results on applying gravity theory to better understand trade costs and suggest improvements for future research. Overall, the paper provides a comprehensive overview of the current state of knowledge and identifies areas for further investigation.This paper surveys the measurement of trade costs, both direct and indirect, and discusses the challenges and recent developments in understanding these costs. Trade costs are significant and vary widely across countries and goods. Direct measures of trade costs, such as tariffs and non-tariff barriers, are limited and often incomplete. Indirect measures, based on trade flows and prices, provide valuable insights but are subject to inference issues. The paper highlights the importance of theoretical frameworks in interpreting and improving the measurement of trade costs. It also emphasizes the role of infrastructure, policy, and economic geography in shaping trade costs. The authors present new results on applying gravity theory to better understand trade costs and suggest improvements for future research. Overall, the paper provides a comprehensive overview of the current state of knowledge and identifies areas for further investigation.