Sediments collected in Kars River were tested for mutagenicity by means of peripheral erythrocyte micronucleus frequency in Orthrias angorae. Micronuclei frequencies (MN) of all the groups exposed to the sediments were higher than those of the control group. Statistical analysis showed significant differences between the control and the treatment groups (P<0.001). The MN frequencies of the blood samples in three regions (Selim, Pasacayir, Bogazkoy) on the day 6 have a trend to increase against to control. MN frequencies of samples collected from 36th hours sediment exposure increased in the three districts (Selim, Pasacayir, Bogazkoy) when compared to control groups. On the other hand there is a decrease in only one region (Kars) at 6 days. This study evaluates for the first time the mutagenic load of sediments collected along the Kars River and provides evidence that the presence of genotoxic agents in river sediments correlates with the genotoxic damage (micronucleated erythrocytes) in fish collected from Kars River.