Hydatidosis is not rare in France and often poses diagnostic problems to practitioners. In addition to classical clinical and radiological data, immunological methods provide at the present time reliable means of confirming the diagnosis and conducting post-therapeutic surveillance. After a brief epidemiological and clinical review, the authors review the different laboratory techniques available and report their experience involving 139 cases collected over a period of 2 years. Emphasis is placed upon the relatively high prevalence of the disease amongst immigrant workers, as oppossed to the rare cases seen in the native population, as well as the value of immunoelectrophoresis and conditioned haemagglutination reactions. New therapeutic possibilities offered by mebendazole and its derivatives are indicated.