To date, proteases were proved useful as candidates for serological diagnosis. In the present work, cathepsin L1 cysteine protease [CL1] of F. hepatica was prepared and characterized. Characterization was done by SDS-PAGE and immunoblot analysis in comparison to F. hepatica excretory secretory antigens [ES] . A complex pattern of bands was shown by ES antigens, while CL1 showed only a prominent zone at 27-29 kDa, which was clearly recognized when probed by sera of Fasciola infected subjects but not with neither sera of S. nansoni infected cases nor normal controls. The protein subunits of the ES antigens that were prominently recognized when probed with sera of proven cases of fascioliasis were 6.5, 12, 27-29, 43 and 112 kDa subunits. Sera of S. mansoni infected subjects could recognize the 12 and 112 kDa subunits of ES antigens, while sera of normal subjects couldn’t recognize any. Moreover, CL1 and ES antigens of F. hepatica together with liver fluke homogenate [LFH] were compared for the serological diagnosis of human fascioliasis by total specific IgG and isotypic IgG4 ELISA. Results showed that CL1 was the most sensitive antigen used on the level of both total specific IgG and isotypic IgG4 ELISA [86% and 96% respectively] . CL1 also showed the highest negative predictive value of 92.6% in specific IgG4 ELISA. Its specificity was 100% without any cross reaction with Schistosoma mansoni infected cases, which is a usual problem encountered with the serological diagnosis of fascioliasis in Egypt. Sensitivity and specificity of ES antigens were satisfactory in case of IgG4 ELISA [92% and 100% respectively] , however in IgG ELISA cross reaction happened with 2 cases of S. mansoni infection. LFH was the least sensitive and specific antigen. So, this study leads to a recommendation of a combination of both Fasciola CL1 as antigen and specific anti- Fasciola IgG4 as the detection antibody in ELISA for diagnosis of human fascioliasis. This would facilitate the diagnosis of obscured cases of f2scioliasis and overcome the problem of cross reaction with S. mansoni infection especially in Egypt where it is endemic and sharing many antigenic epitopes with Fasciola spp.