In the United States, hydatid disease of the liver is being seen with increasing frequency in persons who have immigrated from endemic areas. At the University of California, Los Angeles Medical Center, 24 patients with 46 echinococcal cysts were managed over a 26 year period. Seven patients (29 percent) had cyst rupture: into the lungs in three patients, the biliary tree in two, and the peritoneum and duodenum in one patient each. In recent years, serologic tests, computerized axial tomography, and endoscopic retrograde cholangiopancreatography have greatly aided the diagnosis and management of these patients. Four patients were treated nonoperatively, and 20 patients (with a total of 41 cysts) underwent operation. Cyst management included partial cystectomy in 19 patients, complete cystectomy in 18 patients, left hepatic lobectomy in 2 patients, and marsupialization and removal of hepatic debris from the common duct in 1 patient each. Primary cyst closure, omental packing, external drainage, or cystojejunostomy was individualized on the basis of cyst size, location, secondary infection or rupture, and communication with the biliary tree. Morbidity, including two temporary external biliary fistulas, occurred in eight patients (40 percent) but could not be related to cyst management or preoperative rupture. No deaths occurred in this series.