The relation between the duration of human fasciolosis and development of humoral immune response has not yet been clarified. This study was conducted to investigate the relation between different immunoglobulin isotypes and the period of disease in fasciolosis patients and also to evaluate the diagnostic value of immunoglobulin isotypes. The 50 patients (30 female, 20 male; age range: 18-70 years) included to the study were evaluated in 3 groups (3-6 months, 7-12 months and > 12 months) according to the duration of their signs and symptoms such as abdominal pain, fever, eosinophilia, detection of eggs in stool and radiological findings. An in-house enzyme-linked immunosorbent assay (ELISA) based on Fasciola hepatica excretory-secretory (ES) antigens was used for the determination of anti-F.hepatica specific IgG, lgM, IgA, IgE antibodies. The positivity rates were 100% for IgG, 50% for IgM, 62% for IgA and 42% for IgE. When the relation between disease period and immunoglobulin classes were evaluated, it was observed that in the 3-6 months period, patients IgM, IgA and IgE levels were; 90%, 72% and 54%, respectively; in the 7-12 months period patients IgM, IgA and IgE levels were 35%, 35% and 21%, respectively, in the > 12 months period patients IgA and IgE levels were 50% and 42%, respectively however, no positive IgM level were detected. In conclusion our data indicated that the specific IgM positivity rate was high (90%) in early stage in fasciolosis, gradually decreased (35%) and became negative in late stages of infection. However, IgA and IgE levels revealed no specific relation to the disease period. Specific IgM determination seems to be useful for the differentiation between acute and chronic period of fasciolosis. Further studies are necessary to prove the diagnostic value of specific IgA and IgE antibodies in setting of fasciolosis.