The result of source identification of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs) and dioxin-like PCBs (co-PCBs) in Japanese river water is presented for the first time. River water and atmospheric deposition samples were collected from different locations in Tokyo Metropolis and Kanagawa Prefecture. The river water samples exhibited a range from 190 to 520 pg·l^-1 for total mono through octachlorinated PCDD/Fs and a range from 21 to 220 pg·l^-1 for total co-PCBs. Dichlorinated dibenzo-p-dioxins (DiCDDs) were the most abundant homologue in the river water samples (54-89% of total PCDD/Fs), while monochlorinated dibenzofurans (MoCDFs) were the most abundant homologue in the atmospheric deposition samples (24-51% of total PCDD/Fs). The concentrations of total TEQ ranged from 0.12 to 0.80 pg-TEQ·l^-1 in the river water samples, and total TEQ was dominated by particulate phase PCDD/Fs and co-PCBs, accounting for 62-97%. The congener profiles of the river water were basically similar to those of the atmospheric deposition (combustion). Several congeners in the river water, however, showed significantly higher proportions within each homologue than those in the atmospheric deposition. Part of these results could be explained by the effects of the impurities of triclosan, which is widely used as a germicide and antiseptic. Multiple regression analysis was used to estimate the contributions of different sources to total TEQ in the river water. The result showed that 73-92% of total TEQ originated from a combustion source.