A brief review of the water-hyacinth studies in Portugal is presented. Water-hyacinth is a noxious invader plant on the central portuguese river basins. Its growth and life cycle are reported. The strategy control methods that have been developed since the 80’s are summarized. Finally, an actual water-hyacinth management program carried on in the agricultural region of Lezíria Grande de Vila Franca de Xira, Tagus River, with 470 km of drainage channels is presented as well as its costs.