An ELISA was used to determine the seroprevalence of cystic echinococcosis (CE), caused by Echinococcus granulosus, in representatives of the rural-agricultural, semi-bedouin and bedouin communities of Jordan. The knowledge, attitudes and practices (KAP) pertaining to the transmission of CE in such communities were also investigated. In the ELISA, serum samples from 2388 subjects were tested for IgG antibodies reacting with antigens in crude sheep hydatid fluid (CSHF). The rural-agricultural subjects were significantly more likely to be seropositive (11.4%) than the semi-bedouin (5.0%) or bedouin (3.7%), but male and female subjects were equally likely to be seropositive. Among the rural-agricultural and semi-bedouin subjects, those aged 11-20 years were most likely to be seropositive. Among the bedouin subjects, however, seroprevalence was highest for those aged 31-40 years. When the distribution of 59 seropositive subjects detected within 36 rural-agricultural households was investigated, 12 (33.3%) of the households were each found to have at least two seropositive members. Immunoblotting indicated that 27.1% of the seropositive rural-agricultural subjects showed immunoreactivity to at least one of the CSHF antigen-B components (of 8-12, 16 and 24 kDa). The living conditions, practices and lifestyles of the rural-agricultural, semi-bedouin and bedouin communities favour the spread of CE in Jordan and warrant an effective programme for the control of the disease.