Many serological tests ore widely used in the diagnosis of cystic echinococcosis CE), caused by the larval stages of Echinococcus granulosus. The present study was carried for differentiation between hepatic and pulmonary cystic echinococcosis by Western Blotting (WB). A total of 12 1 sera from patients with hepatic CE (37, pulmonary CE (3 1) and controls 5 3; consisting of six healthy, seven Hymenolepis nono infection, 20 hepatic and 20 pulmonary diseases other than CE) were examined. In all of the CE patients, E. granulosus infection was confirmed by surgical intervention. Sera were previously tested using IHA and ELISA to detect the E. granulosus specific antibodies. Sera from hepatic cases of CE reacted with 16 polypeptides of 6-116 kDa and sera from pulmonary cases of CE reacted with 14 polypeptides of 4-130 kDa by Western Blotting. The WB test enabled the detection of antibodies in the hepatic CF samples for proteins of 24, 32 34, 44-46 and 52-54 kDa in molecular weight in 78.4%, 75.7%, 78.4% and 89,2 % of the patients, respectively. In the pulmonary CF samples sera WB test enabled the detection of antibodies 24, 44-46, 100, 1 10, 1 16 and 120-124 kDo in molecular weight in 81.3 %, 75.0 %, 87.5 %, 71.9 %, 84.4 % and 65.6 % of the patients, respectively. We indicated that the antigenic components of high molecular weight con be good candidates for differentiation of hepatic CF from pulmonary CF.