In order to explore the available sero-diagnotic method for surveillance in basically controlled and controlled areas of schistosomiasis japonica, a 3 years longitudinal investigation of children 6~14 years old with COPT in 5 endemic areas was carried out after being basically controlled for 8~16 years. The results showed that the examination of children with COPT is one of the available serodiagnostic methods of schistosomiasis for surveillance. In all five areas the positive rate of children in this age group was less than 3%, and the circumoval precipitin rate among the positive cases was less than 5%. Therefore, it is indicated that the above mentioned two indexes can be used for sero-surveillance of schistosomiasis japonica.