HYDATID DISEASE, a form of helminthiasis, was described by Hippocrates, and now is known to be widely distributed throughout the world. It is prevalent in South America, Iceland, Australia, and New Zealand, and frequently encountered in the regions along the Mediterranean, and in Central Europe, Russia and South Africa. Native infection in the United States and Canada has been considered very rare. Recent observations indicating the presence of endemic echinococcosis in North America, and the increasing number of immigrants admitted to the United States and Canada from hydatid-infested countries, make imperative the recognition of the disease. Osler in 18821 collected 61 cases occurring in