Background:The aim of this study was to determine the effect of metronidazole in patients who did not cure after treatment with triclabendazole, in Guilan (Northern Province of Iran).Material/Methods:Patients, who passed fasciola egg in stool and had positive serum anti fasciola antibody (ELISA), at least three months after treatment with triclabendazole, were enrolled and received 1.5 g/day metronidazole orally for three weeks. Two months and 12 months after end of therapy, stool examination in 3 consecutive days and serum anti fasciola antibody were performed. Frequency of patients with negative serology for fasciola and/or absence of fasciola egg in stool were determined. Chi-square test was used and P value

Keywords: Anthelmintics - therapeutic use, Antitrichomonal Agents - therapeutic use, Benzimidazoles - therapeutic use, Enzyme-Linked Immunosorbent Assay, Fascioliasis - drug therapy, Feces, Metronidazole - therapeutic use, Time Factors