Among the measures used in attempts to control the snail host of S. japonicum in Leyte Province, Philippines, where the terrain is unsuited to the application of molluscicides, have been removal of vegetation in and around infested streams, drainage of water-logged areas, filling low-lying areas with earth or flooding them, and digging fishponds in sluggish streams. Each of these measures is described in detail.Experiments carried out in rice-fields, which harbour great numbers of snails, have shown that improvements in rice-growing methods will not only markedly reduce the snail population but also double the rice yield.A campaign to promote the use of pit latrines encountered the serious difficulty that such latrines were not acceptable to the people. However, there is evidence that use of pit latrines does bring about a reduction in snail infection rates.No single control measure is recommended for all snail habitats, the choice of method depending on local circumstances; in many areas a combination of methods proved advantageous. It is felt that mass treatment of infected persons would not be fully effective until transmission is more thoroughly under control.