Different probiotic strains are incorporated into cultured-milk drinks by respective manufacturers with the common aim of providing health benefits to the consumers. Four common cultured-milk products (brands N, S, V and Y) were evaluated for their quality of probiotic strains used, based on the susceptibility of the probiotics to various pH levels simulated to mimic the gastrointestinal system. Results showed that brands Y and V have higher initial probiotic inoculum compared to brands N and S although probiotics from brands N and S were more tolerant to pH 3. Generally, all probiotic strains preferred higher pH with highest viability of Lactobacillus spp., Bifidobacterium spp., and Streptococcus thermophilus observed at pH 8.1. Our study also discovered that among the four brands tested, brand V contained probiotic strains which are most likely to remain viable after passage through the gastrointestinal system.