In order to investigate the occurrence and indicator of protozoa in water, water samples were collected from 11 points along the Sagami River and its tributaries for 9 months. The concentrations of Cryptosporidiurn oocysts, Giardia cysts and potential indicators (presumptive Clostridium perfringens spores, Escherichia coli, coliforms, aerobic spores and turbidity) were analyzed. Cryptosporidium oocysts were detected at 10 of the 11 sampling points (GM 34 presumptive oocysts·100l-1, 24 confirmed oocysts·100l-1) and Giardia cysts were detected at all sampling points (GM 30 presumptive cysts·100l-1, 12 confirmed cysts·100l-1). Based on a regression analysis, the concentrations of presumptive C.perfringens spores and E.coli were significantly correlated with the concentrations of protozoa. In a multiple regression analysis, the concentration of presumptive C.perfringens spores, E.coli and aerobic spores were selected as explanatory variables for the protozoan concentrations. The results indicated that presumptive C.perfringens spores, aerobic spores and E.coli were useful indicators for protozoan contamination.
