A total of 2.8% (5 of 176) sera from schoolchildren and university students were seropositive for hydatidosis (Echinococcus granulosus) by the ELISA IgEtest. The prevalence of seropositivity was 4·5% among females of all age groups (5–24 years) and among males of the age group 18–24 years. Males of the age group (5–17 years) were seronegative. The ratio of seropositivity between schoolboys and schoolgirl was 1:4. Sera collected from 1085 university students, aged 18–24 years, and from 1656 outpatients from northern and central Jordan, and the Jordan River valley, when tested by the IHA test, revealed the presence of antihydatid agglutinating antibodies in 5·16% (56 of 1085) and in 3·6% (60 of 1656) respectively, with a male to female infection ratio of 1:3 in the unviersity students and 1:1·1 in the outpatients. Intensity, prevalence and cyst fertility of E.granulosus increased increased in sheep with age. The results of this study indicate that hydatidosis is in an endemic steady state in Jordan with estimated economic losses if JD 3·0 (=US $ 4·4) per infected sheep.