Hydatid disease is an important health problem in areas where it is endemic. There are several therapeutic modalities, the most important being surgery, antibiotherapy, and percutaneous treatment. In recent years percutaneous treatment has become popular, and for this method or surgery it is sometimes lifesaving to know the relation between the biliary ducts and the cyst cavity. The aim of this study was to examine the usefulness of endoscopic retrograde cholangiopancreatography and (99m)Tc-labeled albumin macroaggregates in diagnosing hydatid disease fistulae before percutaneous or surgical treatment. A total of 72 patients diagnosed with hepatic hydatid disease via ultrasound and serologic tests were enrolled in the study. Endoscopic retrograde cholangiopancreatography was successfully performed in all patients. (99m)Tc-labeled albumin macroaggregates also were injected into cysts at a dose of 1.5-2 mCi just before the treatment. All but three patients were treated percutaneously. Scintigraphy of abdominal and thoracic areas was performed with a GE Starcam 3200 XC/T gamma camera at 30 and 120 min after Tc-labeled albumin macroaggregate injections. Endoscopic retrograde cholangiopancreatography revealed communications between biliary ducts and cyst cavities in nine patients (12.5%). However, (99m)Tc-labeled albumin macroaggregates showed not only leakage into the systemic circulation in nine patients but also into the biliary ducts in two (15.4%). In one patient, mild acute pancreatitis occurred as a complication of endoscopic retrograde cholangiopancreatography. No complications of (99m)Tc-labeled albumin macroaggregates injection were seen. Three patients were surgically treated because of clinically manifested cystobiliary fistulae. We conclude that endoscopic retrograde cholangiopancreatography is a gold standard technique for the diagnosis of communication between the biliary duct and the cyst cavity, and (99m)Tc-labeled albumin macroaggregate injection is useful for revealing leakage into the systemic circulation. The diagnosis of biliary fistulae before percutaneous treatment of hydatid disease may enable planning of the optimal therapy.