Abstract: S72014 is a derivative of niridazole. It has been found that the therapeutic index of S72014 to mice was 21.2, while that of niridazole was 5.8. When rabbits infected with schistostomes were treated orally with S72014 at the dosage of 200 mg/kg/day for 2～3 days, or 50～70 mg/kg/day, for 10～14 days, the worm reduction rates were higher than 90%, with part of the animals completely cured. After its administration to infected dogs at the dosage of 41.7 or 66.7 mg/kg thrice daily for 7 days, all the animals were found to be free of worms. The same promising effect was observed in infected monkeys treated with S72014 at the dosage of 70 mg/kg thrice daily for 14 days.The toxicity of S72014 to mice was at least nine fold lower than that of niridazole. In both mice and dogs, the toxic action of S72014 on the central nervous system was less than that of niridazole. After administration of S 72014 to dogs and monkeys, no apparent effect on hepatic and kidney function was observed, but the ECG showed a low voltage in S-T segement and flattened T wave. With bigger dosage of both drugs, reversible pathological lesions were observed in the liver, kidney and central nervous system of the dogs and monkeys, and the spermatogensis of male animals was suppressed significantly. In dogs treated with S 72014 or niridazole twice or thrice daily for 7～14 days, the most serious side effect was aplastic anemia, which, nevertheless, was not observed in monkeys.