The level of detection and the specificity of primers have a great influence on examination results. The aim of the study was to evaluate the primers applied for identification of B. longum, B. breve, B. infantis and B. bifidum – the species most commonly inhabiting the gastrointestinal tract of infants, and also B. lactis strains commonly used in bioyogurt manufacturing. Ten primer pairs were applied in the study, nine of them were previously described by Kok et al. [1996], Roy et al. [1996], Matsuki et al. [1998, 1999], and Ventura et al. [2001], and one pair was original. The specificity and sensitivity of the PCRs were tested using pure reference bacterial strains, followed by studying the freshly isolated strains, preliminary classified due to phenotypic features to B. longum, B. breve, B. bifidum and B. lactis species. The tested primer sets enabled classification of the human-derived strains to B. longum, B. breve, and B. bifidum, as well as B. lactis species with all the primers applied, except for BreU3/BreL5 primer set, which did not give any amplification product with any tested B. breve strain. The primers Bflact2/Bflact5 applied for B. lactis identification yielded additional PCR products with all the strains originating from adults, and belonging to B. longum or B. bifidum species. It was impossible to classify any strain originated from rats with the applied primer sets. The performed PCR amplifications revealed highly significant differences in the detection level, which amounted from 1 pg to 10 ng of the template DNA in the reaction mixture. The performed evaluation can facilitate the examination of complex microecosystems with the tested primers.