A total of 294 one-day old Cobb broiler chickens were used to investigate the effects of four lactobacillus strains on production performance. The chicks were assigned randomly to six groups with 7 replicates of 7 chicks per treatment. The six dietary treatments were: (i) basal diet (negative control, Tl); (ii) basal diet with added Zinc-bacitracin (ZnB, 50 ppm, T2), iii) one of four strains of Lactobacillus (tentatively identified as L. johnsonii, L. crispatus, L. salivarius and unidentified Lactobacillus sp., T3, 4, 5 and 6). The probiotic strains were selected from 235 lactobacilli isolates based on their in vitro antagonistic effect against Clostridium perfringens and Escherichia coli. Results showed that the addition of probiotic Lactobacillus spp. to the feed did not significantly improve body weight gain, feed intake and feed conversion ratio of broiler chickens raised in cages during the 6-wk experimental period.