Abstract: A series of α,ω-bis-(p-aminophenoxy)-alkanes was reported to exhibit high schistosomicidal activity in experimental animals but those compounds are too toxic to be used clinically. In this study, benzimidazole and thiadiazole rings were used instead of benzene ring, mercapto-group was used instead of oxygroup, and six new compounds were prepared as follows: These new compounds, except 1, 4-bis-(5-amino-benzimidazole-2-mercapto)-butane which is to be tested, were found, to be inactive against schistosomiasis Japonica in experimentally infected animals.