Purpose: To evaluate the effects of Wi-Fi and lactic acid bacteria on salivary mutans streptococci and caries formation. Materials and Methods: Wistar rats and their offspring were equally divided into two main groups and seven subgroups. Experimental groups were exposed to Wi-Fi during pregnancy and lactation. Subgroups were divided according the administration of the beneficial bacteria L. plantarum 167.P6.5 and L. rhamnosus M17-10.2. In the 8-week experimental period after weaning at 21 days, Mutans streptococci counts and the number of carious lesions were determined. Results: The MS count ratios at the end of 8 weeks were statistically significantly lower than those at the end of 4 weeks in all groups given L. rhamnosus (p 0.05). A strong correlation was found between the total MS count and sulcal caries scores (r = 0.507). No statistically significant difference was observed between groups exposed to Wi-Fi and other groups in terms of microorganism count and caries scores (p 0.05). Conclusions: These results suggest that lactic acid bacteria, especially those originating from an oral source, may be of benefit as probiotics for the prevention of oral pathogens and dental caries. Perinatal and lactational exposure to Wi-Fi does not predispose to caries development in rats. Schlagwörter: dental caries, electromagnetic radiation, lactobacilli, mutans streptococci, probiotics, tooth