AbstractIn warm climates the control of aquatic snails as intermediate hosts of trematodes is very important for health. A biological control has been successful by a predatory snail (Marisa) as well as by reducing the aquatic vegetation. Of a greater importance, however, still is the chemical control by various molluscicides, especially by cholinesterase inhibitors (carbamates and organophosphorus compounds), which are active also in sublethal concentrations via the carbohydrate and protein metabolism. Of a special importance is also the application of synergistically active compounds, by which the biocidal activity is considerably increased, the required biocide concentration in the water is decisively reduced. Molluscicides of plant origin may be very important in future, especially the later of Euphorbiaceae and the natural products obtained from them which are active at high dilutions. Also the field of chemosterilants need to be explored.