Competitive exclusion for the prevention of intestinal colonization by Salmonella is an attractive approach that showed promise in some animal species. Nurmi and Rantala demonstrated that the susceptibility of broiler chicks to colonization by Salmonella spp. was due to the delayed establishment of intestinal microflora in chickens. They also showed that Salmonella spp. infections could be prevented by feeding the chicks with anaerobic cultures of normal adult fowl flora (Nurmi et all973). Although the efficacy of competitive exclusion has been demonstrated in chickens, little work has been done with other species. Mucosal competitive exclusion was recently used to control Salmonella in swine and tends to reduce the presence of Salmonella in tissues (Fedorka-Cray et al, 1996). Other studies have used well characterized lactic acid bacteria. Shanhani et al ( 1977) reported that lactobacilli could inhibit the growth of Salmonella in vitro. Competitive exclusion of E. coli and other pathogens by lactobacilli and their cell wall fragments has been demonstrated on human cells in culture by several other workers (Chan et al 1985, Coconnier et al. 992). The most commonly used and reported probiotics include lactobacilli (L. acidophilus, L. casei, L. bulgaricus), and bifidobacteria (B. bifidum, B.longum, B. breve, B. infantis) (Saavedra J.M. 1995). One of the proposed mode of action of such microbial preparations is that the component organisms may colonize the intestine, inhibit the growth of pathogenic bacteria such as salmonellae, and establish a more favourable environment in the host animal (Jin L.Z. et al1996). Carrier state of Salmonella in swine productions may result in contamination of meat. Efforts are now being made to control Salmonella infection at farm-level and probiotics seems to be a practical and safe approach. The objective of this experiment was to determine if probiotics used as feed additive influence the colonization of tissues and the shedding of Salmonella typhimurium in experimentally infected pigs.