This survey was conducted to study the seroepidemiology of hydatidosis in northwest of Iran. Totally 852 blood samples from rural inhabitants of Sarab, Meshkin shahr, Moghan and Urmia were collected and their sera were separated. For antigen preparation, the livers and lungs of sheep infected with hydatid cyst and slaughtered at Tabriz abattoir were collected. The protoscolex was separated from the hydatid cyst and injected into the rabbit diaphragm using the sandwich technique. Then sections of the diaphragm were cut using the cryocut apparatus and fixed onto slides. The prepared sections were examined using marked antihuman globulin stained with Evan’s blue by IFA test. Initially sensitivity and specifity of this test was evaluated on sera of 58 hospitalized hydatidosis patients and 70 healthy persons. The sensitivity and specifity of the test were estimated 88% and 98/6% respectively. In this survey the titers over 1:10 were considered positive. Among 852 tested samples, 30(3/52%) were infected. Infection rate in males was higher than females. The highest infection rate was from Meshkin shahr (3.5%) and the age group of 20-40 years was the highest infected category.