ackground: Parasitic cysts of the liver are caused by larval stage of tapeworms Echinococcus granulosus and Echinococcus multilocularis. Diagnosis of human echinococcosis, based on visual techniques (ultrasonography or computed tomography)and serological tests (ELISA,IHA) is sometimes problematic .Recently many authors suggest that fine needle biopsy of cyst in an useful diagnostic tool.The aim of the study was to estimate value of this method in diagnosis of liver echinococcosis. Material/Methods: Between January 1996 and June 2002,48 patients, aged 18 –79 (mean age 54.6)were diagnosed with suspicion of liver echinococcosis n all cases computed tomography of liver and serological tests were performed .In 38 (79.1%)cases fine needle biopsy was done after anti-parasitic pretreatment with imidazole derivates. Results: Cytological examination of cyst fluid revealed:in 4 cases presence of echinococcal material (hooks)and some eosinophilic masses with calcifications;-in 6 cases hyaline material and proteinic masses;-in 18 cases blood elements;-in 7 cases hepatocytes only and in 3 cases -no any material.In 37 patients biopsy was well-tolerated,only one patient manifested a short syncope. Echinococcosis was diagnosed in 12 patients (25%);in three patients diagnosis was established on the base of cytological examination only,with negative serological tests. Conclusions: 1.Fine needle aspiration biopsy is useful in differential diagnosis of echinococcosis, especially in the cases with negative serology.2.Fine needle aspiration biopsy is a safe procedure in patients after pre-treatment with imidazole deriates.