An aircraft observation of atmospheric pollutants was made over the western part of the Sea of Japan based on the IGAC/APARE/PEACAMPOT program on Nov. 11 and 12, 1992. High concentrations of SO2 and NOx were observed, and their distribution showed a clear dependence on wind direction. When wind blew from the west of north west, a very high concentration of SO2 (up to 10 ppb) was observed. The result of back trajectory analysis points to the contribution from industrialized areas of Korea.