Molluscicides have a history of success and failure in schistosomiasis control. High cost of imported synthetic compounds, along with increasing concern over the snail resistance to these compounds and their toxicity in non-target organisms, has given a new impetus to study plants molluscicides. Three screens were developed to investigate new plant molluscicides from family Euphorbiales. In the preliminary screen, the aim was to identify the plants parts which had no molluscicidal activity and those which did to the snail Biomphalaria pfeifferi and allowed for determination of the LD50 and LD90 values. In the secondary screen, the molluscicidal activity was carried out in which factors that affect the molluscicidal performance under field conditions were investigated by laboratory simulation. For the definitive screen, most stable plant molluscicide was examined for its toxicity towards snail egg masses, other snails and non-target organism. Active components came in later stage of definitive evaluation together with studies of toxicology. Histopathological studies of different organs of treated snails were carried out and compared with the normal tissue from control snails.