Abstract: A comparative study on the biochemical parameters in hydatid cyst fluids of sheep, goat, cattle, camel and human cystic forms of Echinococcus granulosus have been made in Mazandaran. Hundred and twelve samples of hydatid fluids were collected from the liver cysts of different hosts (sheep, cattle, goat, camel and human) in slaughterhouses of sari and Ghaemshahr and Immam hospital respectively. All cyst fluids were centrifuged at 4500 rpm at 4�C for 45 min and the supernatants were analyzed for various biochemical parameters. Quantitative variations in the levels of Sodium, Glucose, Urea, Alanin Aminotransferase (AST), were found in the cystic fluids of different host origins although these differences were statistically insignificant. However, differences in the concentration of Potassium, Calcium, Triglycerides, Cholesterol, Uric acid, Creatinin, Albumin, Gamma glutamyl transferase, Aspartat Aminotransferase (AST) and Creatinine Phosphokinase (CPK), in different hydatid cyst fluids were statistically significant. Differences in the biochemical composition of different hydatid cyst fluids suggest existence of more than one strain of Echinococcus granulosus in human and other domestic animal intermediate hosts in Mazandaran.