Cryptosporidiosis is a disease caused by oocysts of Cryptosporidium parvum . In June 1996, about 1, 000 people in Saitama prefecture, Japan, became ill with a prolonged diarrhea after drinking water contaminated with oocysts of C. parvum . Therefore, waterborne cryptosporidiosis is gathering concern in Japan. The diagnostic methods are acid-fast stain and immunofluorescence of oocysts of C. parvum in feces. However, the methods for the concentration and detection of the oocysts in water from private supplies and river water involving many impurities have not been established in Japan. In this study, using the method for the concentration of viruses from water using cellulose, we examined whether the oocysts in river water can be concentrated with DEAEcellulose and eluting solution. The most efficient eluting solution was the solution consisting of 1m l Tween 80 and 10g NaCl in 1 l pH 9 water.