1. The efficacy of a commercial competitive exclusion (CE) product, BROILACT, was tested in pilot-scale trials involving groups of 100 broiler chicks. 2. Each group was challenged with Salmonella infantis through contact with infected seeder birds and numbers of salmonellae in the caecal contents were determined weekly. 3. The performance of the birds was also monitored over a 5-week period. 4. The results showed a gradual decline of the infection, even in the untreated groups, and a dose-dependent response to treatment. 5. The treatment had no significant effect on the performance of the birds.