Fine needle aspiration biopsy (FNAB) was performed in 31 patients with hydatid disease by 15 operators in 41 biopsy events during the period 1983–93. The FNABs were unintentionally done without prior clinical suspicion of hydatid cysts (HCs) in 18 patients and intentionally (with prior clinical suspicion of HC) in 13 patients for pathologic confirmation required for specific therapy. The FNABs were performed with the guidance of fluoroscopy (n=7), CT (n= 14) or ultrasonography (n= 10). The material included both closed, open and ruptured HCs from different locations such as abdomen, thorax, spine and bone. Pathologic confirmation of HC was achieved by recovering and demonstrating parasitic material in the specimen. In only 7 of 31 patients were the specimens diagnostic at the initial interpretation. This emphasizes the importance of alerting the pathologist about the possibility of hydatid disease. In 25 of 31 patients (81%) no biopsy reactions occurred. In 5 patients minor allergic reactions occurred and 3 had filling of air into intrathoracic cysts not requiring therapy. One patient, with a FNAB of a liver HC, had a sudden severe drop in blood pressure, which required anti-shock therapy with subsequent recovery without sequelae. All complications occurred with non-intentional biopsy of HC. Suggestions for diagnostic and therapeutic management of patients with HC and advice to avoid or limit potential complications or spread of disease are given where a planned biopsy is necessary for appropriate and effective therapy.