In an experiment with broilers infected with a rifampicin-resistant Salmonella Typhimurium strain at 15 days of age, it was demonstrated that whole wheat feeding influenced the course of infection. The pH in the contents of the gizzard decreased as the amount of whole wheat in the diet increased over time. Following infection, lower numbers of Salmonella Typhimurium were found in the gizzard and ileum of birds receiving whole wheat compared to pellet-fed birds. However, there was no difference with respect to the numbers of Salmonella Typhimurium in the ceca and rectum between the two experimental groups. Quantitative cultivation of different groups of bacteria belonging to the natural intestinal microflora showed that whole wheat feeding significantly reduced the numbers of Clostridium perfringens in the intestinal tract of the birds. The present results indicate that the gizzard has an important function as a barrier organ, one that prevents pathogenic bacteria from entering the distal digestive tract.