Since 1936, 13 patients (9 men and 4 women) had hydatid cyst disease at the Lahey Clinic. The cysts involved the liver in 11 patients, the spleen in 2 and the brain in 1 patient. All patients had surgery; operations were marsupialization, resection of cyst, splenectomy or craniotomy. Two patients died postoperatively, and 1 patient had incapacitating ascites due to peritoneal seeding after a cholecystectomy.