(Available electronically only) Water hyacinth is widely recognised as the world’s worst aquatic weed. It forms dense impenetrable mats across wsater surfaces, limiting access by man, animals and machinery. Navigation and fishing are obstructed, and irrigation and drainage systems become blocked. The consequences are devasting for those communities reliant on water bodies for water, food, sanitation and transport. Biological control of water hyacinth offers sustainable, environmentally-friendly, long-term control, and is the only feasible method to provide some level of control to those infestations which cover huge areas, are difficult to access and/or do not warrant the high cost of physical or chemical control. This ACIAR publication contains chapters on distribution, habitat, control and looks at the water hyacinth weevils.