The aim of the study was to evaluate the toxic and mutagenic effects of bottled purified and natural spring waters for drinking. The study presents the genotoxicologic results of drinking water samples packaged in polyethylene terephthalate (PET) bottles. Genotoxic agents have the potential to interact with DNA and may cause DNA damage. Endpoints analyzed included mitotic index (MI), replication index (RI), and sister chromatid exchange (SCE). An analysis of variance test (ANOVA) was performed to evaluate the results. A significant decrease in MI and RI was observed compared with negative control cultures, respectively, (p < 0.05, p < 0.01). It is found that SCE frequency increases compared with negative control. There is no significant difference between negative control and drinking water samples and among drinking water samples for sister chromatid exchange induction (p > 0.05). (C) 2008 Elsevier Ltd. All rights reserved.