The comparative sensitivity and specificity of the immunoelectrophoresis (IEP), latex agglutination (LA) and indirect hemagglutination (IHA) tests for hydatidosis were evaluated using a single hydatid cyst fluid pool as antigen and the same hydatid and non-hydatid sera and were found to vary with the type of IHA test, the criterion for IHA test positivity and the group of sera selected for study. The sensitivity of the LA and IEP tests was comparable, both tests correlated well and neither gave a positive result in the non-hydatid sera studied. The sensitivity of the IEP test was higher when IHA test positivity was based on diagnostically significant titers but not when all IHA test reactors were considered as positive to this test. The merits and limitations of the LA and IHA tests in diagnostic and seroepidemiologic studies of human hydatidosis are discussed. On the basis of the present findings, the use of the LA test and possibly of the tannic acid IHA test, to screen for IEP test positive sera is proposed as the most reliable immunodiagnostic approach to estimate the prevalence of human hydatidosis for seroepidemiologic purposes and also for detecting hydatidosis cases in the field.