This study was conducted to investigate the effect of a number of drugs on the viability of primary protoscolices isolated from sheep infected with the larval stage of E. granulosus. These drugs included Oxfendazole (OFZ) at a concentration of 0.05 mg/ml, mixed with Praziquantel (PZQ) at a concentration of 4 mg/ml and Albendazole (ABZ) at a concentration of 1 mg/ml. The results showed that OFZ was the most effective in influencing the viability of the protoscolices. The percentage of killing after five minutes of treatment was 85.63% and it was 17.21%, 15.10% and 13.09% for OFZ+ABZ, OFZ+PZQ and ABZ+PZQ, respectively. After 30 minutes, the killing percentage was 99.04%, 71.63%, 40.19% and 31.09%, respectively. The percentage of killing reached 100% after 35 minutes, 40 minutes, 2 hours and 3 hours, respectively. The results confirm the use of OFZ as a lethal drug, or a viability-suppressant for protoscolices in the future, after conducting more researches to know the side effects of this drug in laboratory animals for access to the best treatment to those infected with hydatid cysts.