A preliminary survey was done in 1980 in Jijiaba Village before the dike was built . The dike of 2. 5 km in length and 4m high was built along Baiyang River by the end of 1980 . The molluscicide NaPCP was used for snail control from 1981 to 1984 . After the entire control measures were completed in 1984, a follow-up survey was conducted as to measure the impact of control measures on prevalence of schistosomiasis and population of snail from 1985 to 1989 . All of the results suggested that these control measures were very successful. The transmission of schistosomiasis in this area has been prevented since 1984 .