Investigations were made in Catende, State of Pernambuco, in order to establish the incidence of infected snails of the genus Australorbis, by cercariae of Schistosoma mansoni, and to test slacked lime and copper sulfate as eradicators of these snails. The high incidence of human infestation by Schistosoma mansoni (50% in more than 300 examinations) is due to the constant use of the rivers, by the population for bathing and other purposes. It was found that slacked lime gives better results than copper sulfate and is also cheaper and more easily obtained. The dilution of lime used was 4 to 5%.