|In this study, 68 water samples were collected for analyzing three types of Total organic halogens (TOF, TOCl, TOBr) in the Lake Biwa ? Yodo River Basin. Survey was conducted on 5th September and 28th November, 2017. Samples were pre-treated by pre-packed activated carbon column (TXAPPC, Mitsubishi Chemical Analytech) followed by removal of inorganic halides using sodium nitrate. Analyses were conducted by combustion ion chromatography (AQF-100F, Mitsubishi Chemical Analytech and ICS-2000, Dionex). Limit of Detections (LODs) of TOF, TOCl, TOBr were provided as 28 ng-F/L, 646 ng-Cl/L, 40 ng-Br/L, respectively. Among total number of samples (68), TOF, TOCl, TOBr were detected above LOD in 67, 42, 64 samples, respectively. Among different water types (Lake water, river water, treated wastewater), on average, TOCl and TOBr were detected at the highest in treated wastewater (36,000 ng-Cl/L and 5,200 ng-Br/L) while TOF was detected at the highest in a specific area, the Ai river basin (22,600 ng-F/L). In addition, algal growth inhibition tests were conducted for some river water (n=12) and treated wastewater (n=8). Growth inhibition rate (median value) was 3.4% for river water while 0.2% for treated wastewater.