Thirty-four strains of lactic acid bacteria (seven Bifidobacterium, 11 Lactobacillus, six Lactococcus, and 10 Streptococcus thermophilus) were assayed in vitro for antioxidant activity against ascorbic and linolenic acid oxidation (TAA(AA) and TAA(LA)), trolox-equivalent antioxidant capacity (TEAC), intracellular glutathione (TGSH), and superoxide dismutase (SOD). Wide dispersion of each of TAA(AA), TAA(LA), TEAC, TGSH, and SOD occurred within bacterial groups, indicating that antioxidative properties are strain specific. The strains Bifidobacterium animalis subsp. lactis DSMZ 23032, Lactobacillus acidophilus DSMZ 23033, and Lactobacillus brevis DSMZ 23034 exhibited among the highest TAA(AA), TAA(LA), TEAC, and TGSH values within the lactobacilli and bifidobacteria. These strains were used to prepare a potentially antioxidative probiotic formulation, which was administered to rats at the dose of 10(7), 10(8), and 10(9) cfu/day for 18 days. The probiotic strains colonized the colon of the rats during the trial and promoted intestinal saccharolytic metabolism. The analysis of plasma antioxidant activity, reactive oxygen molecules level, and glutathione concentration, revealed that, when administered at doses of at least 10(8) cfu/day, the antioxidant mixture effectively reduced doxorubicin-induced oxidative stress. Probiotic strains which are capable to limit excessive amounts of reactive radicals in vivo may contribute to prevent and control several diseases associated with oxidative stress.