There are still many Oncomelania snails that inhabit the Kofu Basin, Yamanashi Prefecture, Japan, which had been declared free of schistosomiasis japonica. Due to the need to monitor the situation, a fixed-point observation system using GIS from GPS is being examined. In addition, in broad present or former endemic areas, survey areas are being managed by remote sensing with satellite images or aerial photographs. A simple and effective monitoring method by mobile GIS using PDAs was developed, risk or hazard maps were prepared and a system that would enable a response in the event of reemergence is being examined.