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A selection of commercial fermented milks was evaluated for the presence and viability of probiotic lactobacilli and bifidobacteria. Counts of Lactobacillus spp. always remained higher than 10⁵ CFUml⁻¹, whereas the population of Bifidobacterium spp. decreased below this level in two products. All the probiotics announced on the label were present in commercial products, yet in two fermented milks one additional group of microorganisms was also found. The yogurt microorganism Streptococcus thermophilus was present in all cases, whereas Lactobacillus delbrueckii ssp. bulgaricus was only detected in two products. Bifidobacterium was the most frequently isolated group, all commercial strains being identified as Bifidobacterium animalis/Bifidobacterium lactis by analysis of partial sequences of the 16 rRNA gene. The same technique allowed the identification of members of Lactobacillus casei (species …