Levels of antibody in sera of 78 patients with opisthorchiasis, 30 patients with other liver diseases, 10 patients with schistosomiasis and 30 healthy individuals were compared using three serodiagnostic tests, namely indirect haemagglutination (IHA), enzyme-linked immunosorbent assay (ELISA) and lectin immuno test (LIT). The geometric mean reciprocal titer in sera of opisthorchiasis patients was significantly higher than patients with other diseases, patients with schistosomiasis and healthy individuals (p less than 0.00001). After treatment with praziquantel, the antibody titers were decreased and became lowest 120 days after treatment. A statistically significant decrease from the pre-treatment sample was observed only at 120 days after infection and not earlier and only with ELISA (p = 0.03) and not with IHA and LIT (p greater than 0.05). Even with ELISA, significant decrease in antibody titer was apparent only when the pre-treatment sera had high enough antibody titer. ELISA was therefore better than the other two tests for the assessment of cure provided that the titer of pre-treatment sera was high.