Using an integrated assessment approach, we evaluate the impact that surface O3 in East Asia had on agricultural production in 1990 and is projected to have in 2020. We also examine the effect that emission controls and the enforcement of environmental standards could have in increasing grain production in China. We find that given projected increases in O3 concentrations in the region, East Asian countries are presently on the cusp of substantial reductions in grain production. Our conservative estimates, based on 7- and 12-h mean (M7 or M12) exposure indices, show that due to O3 concentrations in 1990 China, Japan and South Korea lost 1–9% of their yield of wheat, rice and corn and 23–27% of their yield of soybeans, with an associated value of 1990US$ 3.5, 1.2 and 0.24 billion, respectively. In 2020, assuming no change in agricultural production practices and again using M7 and M12 exposure indices, grain loss due to increased levels of O3 pollution is projected to increase to 2–16% for wheat, rice and corn and 28–35% for soybeans; the associated economic costs are expected to increase by 82%, 33%, and 67% in 2020 over 1990 for China, Japan and South Korea, respectively. For most crops, the yield losses in 1990 based on SUM06 or W126 exposure indices are lower than yield losses estimated using M7 or M12 exposure indices in China and Japan but higher in South Korea; in 2020, the yield losses based on SUM06 or W126 exposure indices are substantially higher for all crops in all three countries. This is primarily due to the nature of the cumulative indices which weight elevated values of O3 more heavily than lower values. Chinese compliance with its ambient O3 standard in 1990 would have had a limited effect in reducing the grain yield loss caused by O3 exposure, resulting in only US$ 0.2 billion of additional grain revenues, but in 2020 compliance could reduce the yield loss by one third and lead to an increase of US$ 2.6 (M7 or M12) –27 (SUM06) billion in grain revenues. We conclude that East Asian countries may have tremendous losses of crop yields in the near future due to projected increases in O3 concentrations. They likely could achieve substantial increases in future agricultural production through reduction of surface O3 concentrations and/or use of O3 resistant crop cultivars. r 2004 Elsevier Ltd. All rights reserved.