An ELIEDA test for hydatidosis was evaluated with sera from preoperative, surgically-confirmed hydatidosis cases, postoperative hydatidosis patients, persons with other parasitic disease and healthy donors. ELIEDA was more sensitive than the counter-immunoelectrophoresis test based on the same positivity criterion and was equally specific for the immunodiagnosis of human hydatidosis. The procedure appears to be simple and rapid and merits consideration in that it determines specific classes of antibodies involved in the immune response which appear to be useful in following the evolution of hydatid cysts.