Twenty strains of Lactobacillus sp., previously isolated from infants’ faeces (MODZELEWSKA et al. 2003) were evaluated for their probiotic properties such as resistance to rifampicin, neomycin, kanamycin, chloramphenicol, ampicillin, penicillin, nalidixic acid, gentamycin, colistin, oxaciclin and nitrofurantoin, survivability in the environment similar to the present in the gastrointestinal tract – pH 2 and 3 and bile salts concentration 1.2, 2.5 and 5%. All strains were resistant to colistin and nalidixic acid and susceptible to rifampicin, nitrofurantoin, chloramphenicol and ampicillin. Strains showed high survivability in pH 2 and 3. After 6 h incubation bacterial counts were at the level of 8.3-7.2 log cfu cm⁻³ compared to initial 8.7-7.2 log cfu cm⁻³. In the environment containing 1.2-5% of bile salts bacterial counts after incubation were from below 1 to 6.6 log cfu cm⁻³. Nine strains, which survived in the highest numbers in bile salts solutions, were considered as capable of surviving passage through the gastrointestinal tract, which is one of the basic requirements which probiotic strains must fulfil.