History and Objectives: Due to side effect and varied prevalence and lack of information on the spread infection of the hydatid cyst in the region, the present study was conducted in urban and rural region of Hamadan in 1991.

Materials and Methods: On 1530 inhabitants covered by urban and rural health and hygiene system, a descriptive study was conducted. Information related to age, sex, location of inhabitant and occupation were recorded. Blood samples (5ml) were obtained and Casoni skin test was performed on all individuals. Antibodies against parasite were measured by IFA method. Titration of 1/10 was taken as positive and for positive blood test higher titration were tested. IHA test was done on positive samples to confirm the results. Titration of 1/64 or higher was taken as positive in IHA test. Prevalence and confidence interval was determined.

Results: From 1530 samples, 64 samples (4%) were positive by IHA test (CI=2.2-3.8). Rate of infection in males and females were 2.9 and 3.1 percent respectively. Rate of infection for urban and rural regions were 3.4% (CI=2-4.8) and 2.7% (CI=1.6-3.8). Tests performed by IFA and IHA indicates that infection among females are more prevalent that in males.

Conclusion: The present study indicates that the rate of hydatid cyst infection is rather high in the region. Therefore, attention should be paid especially to the female inhabitants. Preventive measures and control through institutions that are responsible and basic hygienic educational programs and control of runaway dogs are needed in order to reduce the rate of infection.