The efficacy of moxidectin at 0,2 mg kg-1 live body mass against the multiple anthelmintic resistant White River Krtz strain of H. contortus was determined and compared to that of ivermectin, a benzimidazole, a salicylaralide and levamisole. Moxidectin and levamisole were effective against this strain of H. contortus and reduced the arithmetic mean burdens of this parasite in the sheep by 99,98% and 99,59%, respectively, while the efficacy of ivermectin, albendazole and closantel was only 29,1%, 33,75% and 78,3%, respectively.