Statement of the Problem: Dental caries is the most common disease of childhood. Using probiotics has recently been introduced to reduce the incidence of dental caries.It consists of live microbial food supplements that beneficially affect the host, and hence are considered an alternative way to eradicate the infections.Purpose: The aim of this study is to evaluate the effect of consumption of probiotic yogurt on the children’s salivary cariogenic microflora.Materials and Method: A double-blind randomized study was performed recruiting 2 parallel groups; 24 healthy children in the case and 25 children in the control group. All healthy children were followed- up over 4 periods. Periods 1 and 3 were wash-out periods with duration of 1 and 2 weeks, respectively. During periods 2 and 4 (2weeks duration each), the case group consumed 200g yogurt containing Bifidobacterium lactis (1×106 per gram) once daily and the control group consumed normal yogurt. Salivary Streptococci mutans and Lactobacilli were enumerated before and after the yogurt consumption periods. Pre- and post-treatment values within and between regimens were compared using the t-test and paired samples.Results: There was a reduction in Streptococcus mutans and Lactobacillus counts in the control group, but for Streptococcus mutans, the count reduction between phases 1 and 4 was statistically significant (p= 0.009). In the case group, neither the Streptococcus mutans count nor the Lactobacilli count was significantly reduced.Conclusion: Based on the findings of this study, short-term daily consumption of probiotic yogurt containing Bifidobacterium lactis could not reduce the levels of salivary Streptococcus mutans and Lactobacilli in 6 to 12 year-old children, while normal yogurt could reduce the Streptococcus mutans counts significantly.