Lactobacilli have been evaluated for their probiotic properties since the beginning of the 20th century. Many reports have focused on the use of lactobacilli for their beneficial, probiotic effects upon the health and well being of humans and other animals. One potential application for lactobacilli in swine is a pre-harvest method to reduce Salmonella. Non-typhoidal Salmonella are associated with 1.4 million cases of foodborne illness in the United States per year. Moreover, pork products are estimated to be the source of 6-9 percent of foodborne salmonellosis in the United States. The experiments described in this thesis evaluate feeding various preparations of yogurt cultures from two isolates of Lactobacillus as a method to reduce levels of Salmonella Typhimurium in swine. In two of six trials, feeding live Lactobacillus paracasei subsp. paracasei GS-1 yogurt cultures significantly reduced levels of Salmonella Typhimurium in tonsil and fecal samples from swine. The Lactobacillus strains used in animal studies were further characterized in vitro. Bacterial strains were developed as tools for future studies in vivo of probiotic mechanisms and sources of variability that influence the probiotic effects of lactobacilli.