Abstract: In the experiment, each of Mebendazole, Albendazole and mixture of them had been applied to feed 105 albino rats infected by Iricki-nella sprialis constantly by 300 ppm mixed with feed. At the different period, how long to apply medicine to the rats was not same. The experiment showed that the mixture of Mebendazole(150 ppm) and Albendazole(150 ppm) was the best to kill T. spiralis at the different infecting period. Next was Mebendazole. To kill muscle T. spiralis at the different infecting period, the time to apply drugs to the rats more economically was from 40 to 90 days after infecting through striped muscle by 2343 cysts per gram. The drugs had been applied for 10 days or from 90 to 165 days, 2080 cysts per gram. The drugs being applied for 15 days or more than 165 days, 2080 cysts per gram, the drugs being applied for 20 days.

Key words: T. spiralis muscle larva, Mebendazole, Albendazole, Albino rats, Larviclde effectiveness