The prevalence and distribution of Echinococcus granulosus in sheepdogs was studied in 13 provinces of Iran, where 90% of the Iranian sheep and goat populations and, thus, sheepdogs are found. Worms were found in 27.17% of 390 dogs successfully purged with 4 mg/kg arecoline hydrobromide. The highest prevalence was detected in dogs from the rural areas of Isfahan (central part of Iran) and the lowest, in dogs from those of Sistan (Southeast Iran). The frequency distribution of E. granulosus was overdispersed, with only a few animals harboring heavy infections.