In this study, the frequency of micronuclei and nuclear abnormalities caused by environmental pollutants were determined in Pelophylax ridibundus from the Biga Stream (Canakkale, Turkey). Healthy and mature animals were collected by hand capture method from along the four stations (estuary zone, city center, buffer zone and industrial zone) of Biga Stream. Blood samples of the live specimens were obtained in the laboratory within one day of their capture. Two peripheral blood smears for each sampled specimen were prepared on clean slides, fixed with methanol for 15 min and dyed with Giemsa stain. Micronuclei and other nuclear abnormalities such as kidney shaped nuclei, lobed nuclei, and notched nuclei and blebbed nuclei were determined and scored in the slides. Also, heavy metal analysis was carried out to determine the pollution level of the waters in the stations. Our result have shown that the frequency of nuclear abnormalities were highest in Station 2 (8.64 +/- 0.51). However, the station 2 has higher rates of values of Al, Cu, Zn and Fe than the values obtained from the other stations. The results have showed that the amount of heavy metals contained in the stations was found to be close parallels with the percentage of the total nuclear abnormalities and each kind of abnormality in P. ridibundus erythrocytes. The results have indicated that the levels of genotoxic pollutants in different regions of the Biga stream differ and lead to DNA damage on the organisms.