Typical Kosa aerosol was sampled on April 18-20, 1988 at Yaku Island about 60 km SW from the Kyushu Island and about 900 km from the nearest coast of China. The Kosa aerosol was found mainly in the coarse size fraction and showed a highly uniform chemical composition irrespective of particle size. The mineral compositions were close to those in the surface soil in the arid area in the north China. The water extract of the Kosa aerosol showed alkaline reaction, which was attributed to dissolution of calcite mineral (CaCO₃). Kosa episode occurs in the spring and seems to have favorable affects to most vegetations as they accerelate biological activity in that season. The total amount of the cations, which are transported as Kosa aerosol and spread over Japan, can be estimated at 4000 eq./ (km² ·y). Therefore, the Kosa aerosol can be expected to protect, at least partly, against the damages of soil and vegetation associated with the acid rain/deposition.