The work gives the data indicating the ability of water sampled from different sources of South Priaralje to induce chromosomal abnormalities in somatic and sexual cells of mammals. It has been shown also that the studied water samples can exert modifying effects on the clastogenic activity of supermutagen nitrosomethylurea. Season-dependent fluctuations of level of spontaneous and induced mutations have been revealed in three tissue systems (liver, cerebellum, and spermatogenic epithelium).