Abstract: A study on seroepidemiology of schistosomiasis japonica was performed by means; of IHA test with a gut-associated antigen of the adult worms among populations in one actually endemic area and two previously endemic, but now controlled areas of the infection. To explore the relationship between the age distribution of antibody response and the transmission of schistosomiasis in populations living in these areas with different endemicity, the graphic distribution curves of antibody levels according to age grouping were drawn. The age distribution curves of antibody levels in populations studied showed different patterns. It was suggested that in a given area, the level of antibody response of individuals in the youngest or younger age group could more likely reflect transmission in recent time and the analysis of antibody level of low age groups could provide a basis for evaluating whether the transmission had been interrupted or not.