This study aims to investigate organic compounds and its toxicity by Ames test and chromosomal aberration in the water of the Nak Dong River. Six sampling sites such as Goryung, Hagueun, Maelie, Duksan, Haedong and Myungiang were selected for these pur15oses. 200 l water samples were absorbed on XAD-2 resin columns (2.5X30cm), eluted with organic solvents mixture of acetone: cyclohexane and then dried under vacuum condition. The extracts from the XAD-2 resin was injected into GC/MS and 184 organic compounds were identified such as aldehydes, aromatic compounds, ketones, phenols, hydrocarbons, alcohols, carboxylic acids, alkanes and some unknowns. The US EPA priority pollutants such as naphthlene, bis(2-ethylhexyl)phthalate and other pollutants, 1,2-diethyl benzene, 1,2,3,4-tetrahydronaphthalene and cyclohexanol were detected in these samples. The concentration of chemical pollutants such as 1,2-diethyl benzene, nephthalene, 1,2,3,4-tetrahydronaphthalene, bis(2-ethylhexyl)phthalate and cyclohexanol were ranged into 1.228 $mu$g/l, 298 $mu$g/l, 30.191 $mu$g/l, 1.147 $mu$g/l and 2.839 $mu$g/l, respectively. The mutagenic activity of XAD-2 extracts were tested on Salmonella typhimurium TA 98, TA 100, TA 1535 and TA 1537 and then exhibited strong mutagenic activity against S. typhimurium TA 98 and TA 100 in the presence of S$_9$. Amon them, bis(2-ethylhexyl)phtalate and 1,2-diethyl benzene showed the most strongest mutagenic activity against S. typhimurium TA 98 and TA 100 in the presence of S$_9$. On the other hands, chromosomal aberration of XAD-2 extracts in the human blood cells were not occurred by the sampling water at Goryung, Hagueun, Maelie and Duksan, Chromosomal aberration were also not occurred by the each concentration of 0.05, 0.1 amd 0.3 mg/l of each 1,2-diethyl benzol, bis(2-ethylhexyl)phthalate, naphthalene, phenol, cyclohexanol and benzothiazol test solution.