The objective of the session was to describe procedures used in the estimation of economic cost of air pollution to agriculture in the U.S. and to present some examples of those estimates. In recent years, there has been great interest in the development of monetary estimates of losses due to air pollution, yet these estimates have varied greatly. Monetary estimates require evaluation of air quality using measures that are relevant to effects on crop yields. The papers presented advance our understanding of the process by which monetary estimates are derived. They demonstrate that greatly improved estimates of the economic impact of air pollution on agriculture are needed.