Background: The purpose of this study was to assess the possible alterations of the levels of plasma NO derivates which are thought to reflect the immune status of the body against cystic echinococcus ( CE). Materials and Methods: Plasma NO2 and NO3 levels of 95 patients with CE were analyzed before treatment and then after a 1 year. All patients were classified according to the WHO-IWGE classification of cystic hydatid disease. The levels of NO2 and NO3 were detected from sera by using a photometric endpoint determination on the basis of absorbance in the visible range at 550 nm. Results: Pretreatment levels of plasma NO2 and NO3 of the CE group were significantly higher than those in the control group ( p < 0.001). However, the posttreatment NO2 and NO3 levels of the CE group were significantly lower than the pretreatment levels ( p < 0.001). Hence, a positive correlation was found between fertile capacity of CE and the levels of NO2 and NO3 ( p < 0.05). Conclusion: The analysis of the levels of plasma NO derivates should be considered for the at preoperative detection of hydatid disease and postoperative follow-up in addition to radiological and serological methods.