The effect of Lactobacillus acidophilus and Streptococcus faecium bacteria on selected blood and meat indicators of broiler chickens was determined. The studies were carried out on 1200 Hybro G chickens reared on litter until 49 days of age. The chickens received the probiotic (250 mg/kg) for either the whole rearing period (group I), from days 1 to 21 of age (group II), or from days 22 to 49 of age (group III). There were no significant differences in body weight or feed conversion among the groups. At 49 days of age, the chickens given the probiotic up to 21 days of age had significantly lower plasma protein, total cholesterol and HDL levels and significantly higher water binding capacity of white meat compared with the other groups. The meat of chickens given the probiotic for the whole period of rearing had a significantly higher protein content, while their crude fat and total cholesterol contents tended to decrease.