It is well known that varieties of biological organisms are spreading to and breeding in oceans far from their original ecosystems. There are also cases reported of harm to humans as a result. In order to address this problem, the International Convention for the Control and Management of Ships' Ballast Water and Sediments was adopted at the International Maritime Organization in 2004. Since the Convention came into effect, new restrictions on the release of ballast water have been implemented. This article discusses the problems associated with the transfer of ballast water as well as the Convention adopted to deal with them.