Air quality in East Asia could deteriorate considerably as a consequence of accelerated development of fossil fuel systems and high economic and population growth rates. Frequently, on clear spring days large scale wind systems develop and transport pollutants from the Asian continent towards the Northwestern Pacific Ocean. On these high-concentration days, a yellow sand event shows good evidence of long range transport from the continent toward the Northwestern Pacific Ocean occurs. In the present paper, an Eulerian transport/chemistry/deposition model of regional-scale is developed to obtain the concentration changes of air pollutants over this area and a series of numerical simulations are carried out for clear springtime high-concentration air pollution epiosodes, mainly from 31 March to 3 April 1993. A field observation is also carried out to measure the concentration of air pollutants at three sites in Yantai (China), Cheju island (Korea) and Kagoshima (Japan) in 1993, 1994 and 1996. At first, from a detailed comparision of the simulation results with the field observation and monitoring data in the East Asia, the validity of the present numerical model is confirmed. Secondly, by numerical simulation, the formation of a highconcentration air pollution belt in East Asia, connecting the eastern area of mid-China, the southern area of Korea and the western area of Japan is shown clearly. In particular, the trospheric ozone concentration in this belt area is found to be remarkably high and a high ozone, concentration at the level of Japanese Environment Standard or more, results in Japan and the Northwestern Pacific Ocean through long range transport from the continent.