The aim of this study was to investigate the prevalence of cystic echinococcosis (CE) of slaughtered sheep and goats in Ahar Abattoir, Northwest of Iran. Out of 7.868 slaughtered animals examined for CE (hydatidosis) in liver and lungs (7.654 sheep and 214 goats), 25.40% were infected. The rates of lungs and liver CE were 15.28% and 6.08% in sheep, respectively, and 19.15% and 10.28% in goats, respectively. The infection rate was higher in lungs and was more pronounced in goats. Existence of infected stray dogs in grassland and ruminant grazing on infected pasture are two main reasons for high infection rates in Arasbaran region.