The objective of the present study was to evaluate the influence of a probiotic product (composition: Lactobacillus acidophillus (3.5 × 10(11) CFU), Streptcoccus faecium (3.5 × 10(11) CFU) and Bifidobacterium bifidum (3.5 × 10(11) CFU)) on broiler performance. A total of 1200 one-day-old broilers were reared until 42 days of age, and distributed in a completely randomized experimental design with 3 treatments (antibiotic, probiotic and control) with 10 replicates of 40 birds each. Weight gain, feed intake, feed conversion ratio and mortality were evaluated. Concerning weight gain, in the periods of 0-7 and 0-14 days of age, the group fed the antibiotic product presented higher values as compared with the other treatments. However, in the periods of 0-21, 0-28 and 0-35 days of age, birds fed the antibiotic presented higher weight gain only in relation to the control group. Feed intake differences were detected only in the initial period of 0-7 days of age, with the group fed the antibiotic product presenting higher feed intake as compared with that fed the probiotic product, although these groups were not different from the control group. No statistical difference was detected in feed conversion ratio among treatments in any of the evaluated age intervals. Mortality was different only in the period of 0-14 days of age, which was higher in the control group as compared with that of the birds fed the probiotic product, but it was not different from the group receiving the antibiotic. Treatment with probiotic product containing Lactobacillus acidophillus, Streptococcus faecium and Bifidobacterium bifidum does not affect broiler performance.