Abstract: Tribendimidin, an analogue of amidantel,was synthesized by this institute. Its antheU mintic effects on rats infected with Nippostrongylus braziliensis, dogs infected with An-cylostoma caninum and hamsters infected with Necator americanus were evaluated in comparison with mebendazole, pyrantel pamoate and amidantel.When rats infected with Nippostrongylus braziliensis and dogs infected with An-cylostoma caninum were treated with tribendimidin at a single oral dose of 25mg/kg, the worm reduction rates were 99.3 and 91.9%, respectively. At the same dosage all Toxo-cara canis in dogs and a part of Syphacia mesocriceti in hamsters were expelled. The oral dosage of tribendimidin needed to cure hamsters infected with Necator americanus was 150 mg/kg.It was found that tribendimidin had the advantages of higher efficacy, lower dosage and shorter course of treatment. All parasites were expelled quickly after treatment. No indication was found of neither mutagenic nor teratogenic effect of tribendimidin.