Abstract: Comparison of Avidin/Biotin-HRP Complex (ABC) with conventional ELISAs has been undertaken in parallel for the detection of anti-SEA antibody level in sera of 36 S. japonicum ova positive, 51 S. japonicum miracidia positive and 34 uninfected normal cases. For each sample, comparison of the two methods is conducted on the same micro-liter plate for reliable data. Results revealed a higher sensitivity in ABC-ELISA than in conventional ELISA with 4-8 folds increase in titer in majority of samples, which accounted for 83.3% and 65.3% respectively in ova-positive and miracidia-positive groups. The fact that one ELISA-negative from the former and two from the latter groups implied that positive reactions in ABC-ELISA do indicate a significantly higher sensitivity of the ABC assay. Among cases with higher ABC-titers, greater percentages were found in patients with lower ELISA-titers. No false positive reaction was observed in sera of 34 uninfected cases by either method. The present results indicated that ABC-ELISA may offer a new powerful tool for the diagnosis of schistosomiasis japonica with higher sensitivity and unaltered specificity. The method may be particularly helpful to identify cases with lower immune responsiveness.