This paper describes the effectiveness of ABZ, ABZ.SO and ABZ + ABZ.SO treatment in mice infected with Echinococcus granulosus protoscoleces. The results were evaluated in two ways: measuring the number and wet weight of developed cysts and by transmission electron microscopy (TEM) of tissue cyss. ABZ and ABZ + ABZ.SO had an important effect upon larval growth in E. granulosus. The ultrastructural changes noted were: vacuolation of tegumentary cells of the germinal membrane; increased number of mitochondria; increased number of autophagosomes and an increase in lipid deposits.