Coprological analysis is still commonly employed to diagnose human fasciolosis despite the fact that this method is not utterly reliable. By far serologic methods in this case hold more validity and reliability. The purpose of the present study was to evaluate a 35-mer peptide covering a preliminary epitope of Cathepsin L1, a new purified antigen of Fasciola hepatica, by IgG-ELISA method for diagnosis of human fasciolosis. The advantage of this method is that identical batches of a synthetic peptide could be generated immediately without any variation in prepared batches and can be applied to diagnose thousands of infection cases assertively. Totally 90 individuals coprologically positive for fasciolosis and 15 control negative serum samples were included in the test. The cut-off value (O.D.450 nm; 1:1250 serum dilutions) with this peptide was 0.16. Considering this value 27 cases of false negative were detected; hence the calculation of the sensitivity of the IgG-ELISA was identified as 77%. No cases of false positive were spotted. It is concluded that this peptide is not capable to detect antibody in patients’ sera. With reference to other peptides some measurements are being put into operation.