Abstract: Fifty-two derivatives of nithiocyamine (amoscanate) were synthe sized. The results of experimental therapy of Schistosomiasis japonicum in mice revealed that eight compounds, 2, 23, 26, 31, 32, 39, 40 and 46, were active. Six of them, 2, 23, 26, 31, 32, and 46, were tested in infected rabbits, the results showed that compound 23 wsa more active than nithiocyamine. Furthermore, these compounds have been submitted for experimental test on filariasis in cotton rats, the results revealed that compounds 2 and 26 were antifilarial, especially compound 26 whcih was shown to be effective against microfilariae as well as adult filariae, and was comparable with heterazan (diethylcarbamazine).