To clarify the current status of ballast water and aquatic organisms in the water transferred from and to Japan, available information on the transferred volume of the ballast water and the migration of aquatic organisms in Japan was reviewed and summarized. It was made clear that Japanese export of ballast water is approximately 30 folds of its import, showing that Japan is an export surplus country of ballast water. Among various organisms migrating with the ballast water, molluscs and crustaceans were found to be the most substantial. We stress the importance of repeating this kind of revewing research after the implementation of the Ballast Water Convention （International Convention for the control and
management of Ship's Ballast Water and Sediments）, and can evaluate the effect of the treaty.