This book included preparation of hydatid antigen from hydatid fluid collected from Echinococcus granulosus cysts found in camels and humans. Six types of hydatid antigens were applied for immunodiagnosis of hydatid disease in a batch of sera collected from 93 cases. Characterization of the affinity purified hydatid fluid antigen was performed using SDS-PAGE & EITB. ELISA test was performed to detect different anti-hydatid antibodies (IgG, IgM and IgA) using different preparations of the camel and human antigens. Also sandwich ELISA was performed to detect hydatid circulating antigen using anti-rabbit Con-A purified camel and human sera. Based on the results of the present study, we concluded that the specific protein bands are 55, 80 and 110 kDa. During detection of anti-hydatid antibodies, the highest sensitivity & specificity were recorded when using crude antigens and host (human) free hydatid antigen, respectively. During detection of circulating hydatid antigen, the sensitivity was found low. This may be due to immune complex formation as well as the chronic nature of the disease, while the specificity is higher with better results when using antigens from human source.