Strains of Lactobacillus delbrueckii ssp. bulgaricus (14 strains) and Streptococcus thermophilus (10 strains) were isolated from traditional hand-made yogurts, in order to select the most suitable strains according to their metabolic activities including probiotic properties. The amount of produced D- or L-lactic acid and hydrogen peroxide of these strains were determined. Also antimicrobial activity and antibiotic resistance were studied. Different amounts of D- or L-lactic acid were produced by strains studied; however lactic acid levels were 0.030-0.1 g/l. While S. thermophilus T13 has not shown any hydrogen peroxide production, L. delbrueckii ssp. bulgaricus G12 strain had a maximum hydrogen peroxide production (8.5 mu g/ml). Moreover, L. delbrueckii ssp. bulgaricus and S. thermophilus strains were resistant to ofloxacin which is an inhibitor of DNA synthesis. Antimicrobial effects of L. delbrueckii ssp. bulgaricus and S. thermophilus on Escherichia coli ATCC 11230, Staphylococcus aureus ATCC 25923, Aeromonas hydrophila 106, Micrococcus luteus NRLL-B 4375, Pseudomonas aeroginosa ATCC 29212, Bacillus cereus RSSK 863, Yersinia enterocolifica ATCC 1501, Salmonella enteriditis RSKK 171 were also determined by an agar diffusion method. All of the L. delbrueckii ssp. bulgaricus strains showed antimicrobial effects against A. hydrophila 106 and P aeroginosa ATCC 29212. S. thermophilus strains did not inhibit the growth of the test bacteria.