Ballast water provides stability and manageability of the ship during sailing, loading and unloading of cargo. Organisms brought through ballast water can be invasive to the new ecosystem, can ruin biodiversity and become a threat to plant and animal communities, especially the human body. This final paper deals with ballast water problems in the Adriatic Sea. Due to their geomorphologic characteristics, semi-rigidity, slow circulation of sea currents and important maritime routes, the Adriatic Sea is considered to be an extremely vulnerable area polluted with ballast water. Alohton's organism, as well as its influence, have already been recorded in the Adriatic. Mnemiopsis leidyi, Muggiaea atlantica, Sphyraena viridensis are just some of the new species of Adriatic ecosystems that, by the absence of their predators, and by adapting to a new habitat, increase their populations by changing the food chain in the Adriatic Sea. A number of legal regulations on ballast water issues have been adopted with the aim to reducue the influence of he impact of the ballast water intake into new ecosystems.