Echinococcus granulosus is the most important species affecting humans leading to unilocular Hydatid disease. Hydatidosis is asymptomatic over a period of time till the cysts reach considerable size and produce symptoms. 90% of the infections can be diagnosed by serological methods but species differentiation is not possible. Positive results imply immunity or previous exposure to Echinococcus. False negative results are obtained when the cysts are calcified. False positive results may occur in cases of cross reactions to infection with other parasites like Filariae and Fasciola.