Since 1998, Japan Soap and Detergent Association has been continuously evaluating the concentrations of four surfactants used in household detergents and fabric conditioners in river surface water: linear alkylbenzene sulfonate (LAS), polyoxyethylene alkyl ether (AE), alkyldimethylamine oxide (AO) and dialkyl dimethylammonium chloride (DADMAC) in Japanese urban rivers, in order to assess the risks of surfactants on aquatic organisms. Surfactant concentrations in the river water in June and September were found to be lower than those in March and December, the season where water temperature is lower, suggesting that the rates of biodegradation in environmental water differ depending on the water temperature. All the measured surfactant concentrations were below the reported predicted no-effect concentration (PNEC) and have been decreasing year by year; suggesting that surfactant risk on aquatic organisms in Japanese rivers is low under current conditions.