The Asian dust (called "kosa" in Japan) transported from desert areas in the northern part of China often covers over East Asia in the late winter and spring. It is not as yet clear when and where sand dust particles were released and through which paths they were transported to other countries. In this study, a method for estimating the released region and time of Asian dust using the long-range inverse transport model of dust particles is described. After that, the global mass distribution of Asian dust is determined such that the regions of the high concentration of Asian dust obtained from the long range transport simulation almost correspond to the observed data at ground stations and dust clouds appeared in MODIS images. The method proposed in this study was applied in case of "kosa" phenomena observed at meteorological stations in Tohoku and Hokkaido districts, Japan on March 17, 2002. As a result, it was found that dust particles were released during about 17 hours from 6h on March 15 in the neighborhood of (43/spl deg/N, 114/spl deg/E).