The objective of this study was to compare the efficacy of albendazole and oxfendazole in the treatment of cystic echinococcosis using naturally infected sheep and goats. Fifteen animals with natural infections of cystic echinococcosis were randomly divided into 3 groups of 5 animals each. Two groups were treated orally with either albendazole or oxfendazole at 30 mg/kg body weight twice a week for 4 weeks; a third group served as controls. Ultrasound and postmortem examination of the animals, as well as microscopic examination of protoscoleces for eosin dye exclusion and flame cell motility, were used to determine the efficacy of the 2 drugs. Ultrasound examination revealed that 4 animals in the albendazole group and 3 in the oxfendazole group had decreased cyst viability (P< 0.05).