Eosinophils and their granules were shown to be significant participants in the inflammatory processes of various helminthic infections. So far, only few reports have dealt with ECP level in parasitic diseases. So, this study aimed at evaluating the serum ECP in fascioliasis and hydatis disease and to compare the ECP level with the blood eosinophil count and serum lgE antibody levels in both diseases. Material and methods: this work included 90 individuals [30 patients with fascioliasis [group I], 30 patients with hydatid disease [group II], and 30 normal persons as control group]. All patients were free from concomitant parasitic infections, viral hepatitis B or C, allergic and autoimmune disorders. ECP was estimated in all patients and controls by radioimmuno assay. Moreover, peripheral blood eosinophil count and serum lgE were also estimated. Results: the mean serum level of ECP was significantly higher in patients with fascioliasis and hydatid disease [31.1±21.4, 20.3±11.6 µg/L, respectively] than the control group [7.1±4.0 µg/L], P=0.001 in each case. Moreover, ECP was significantly higher in fascioliasis group than in hydatid group [P=0.001]. The mean eosinophil count was 3.1x10⁹/L ±2.2 in patients with fasciola infection, 1.4x10⁹/L ±1.0 in patients with hydatid disease, and 0.2x10⁹/L ±0.1 in the control group. Serum level of lgE antibody was found to have a mean value of 178.9±66.7 IU/ml in patients with fascioliasis, 157.9±54.1 IU/ml in patients with hydatid disease, and 90.9±35.5 IU/ml in the control group. ECP was shown to have significant positive correlations with the peripheral blood eosinophil count in both groups of patients. However, it was more significant with fascioliasis, a disease with more degree of eosinophilia. In contrast, no significant correlations existed between ECP and lgE antibody in either the groups. Conclusion: The data indicate a generally greater activity of the eosinophil cell system in fascioliasis and hydatid disease. So, ECP appears to be a useful clinical parameter in parasitic infections with eosinophilia to assess disease activity, inflammatory process, or may serve as a new tool for monitoring therapy.