Hydatid cyst of the liver is not uncommon in France. Its various symptoms often include pain, but chance discovery is not exceptional. The diagnosis is helped by two paraclinical examinations, ultrasonography and computerized tomography, which have become indispensable as they provide invaluable information on the precise location and anatomical rapports of the cyst and on possible complications. Laboratory tests are useful for the diagnosis and post-operative follow-up of these cysts. For the time being at least, treatment is purely surgical. Percutaneous needle aspiration and drainage have not yet proved to be totally innocuous, and medicinal treatments seem to be helpful only in cases with intraperitoneal rupture. The choice of the operative technique--essentially a more or less complete cystectomy--has an impact on surgical results: the operative mortality is usually low (2 to 5 p. 100), but the morbidity, mainly due to biliary tract complications of the cysts, remains as high as 30 p. 100.