In this study, the viability of free and immobilized forms of Streptococcus thermophilus A21 and W22 was evaluated in terms of their tolerance-of low pH, bile salts and resistance to nisin and penicillin G. The immobilized strains were more resistant to low pH and to bile salts than free strains. Besides, immobilized strains found resistant to nisin and penicillin-G. When compared the amount of L(+) lactic acid and EPS produced by both free and immobilized strains, the decrease of L(+) lactic acid and EPS production in the immobilized strains were found to be insignificant. However, during a two week's storage period at refrigerator and room temperature, there were no significant differences in the viability of immobilized A21 and W22 strains. The results of this research show immobilization of the cells did not impair, or even improved, the probiotic and technological properties of tested strains.