Listeria monocytogenes is food-borne pathogen that causes listeriosis in individuals with a compromised immune system and pregnant women. This pathogen can survive in anaerobic conditions present in specially packaged foods as well as the gastrointestinal tract. The purpose of this study is to evaluate virulence of L. monocytogenes F2365 in anaerobic conditions. Another goal of this study is to establish gerbils as the ideal animal model since descrepancies exist in current models. Gerbils were orally infected with one of four doses: 1) phosphate buffered saline, 2) 5X106CFU aerobic dose, 3) 5X108CFU aerobic dose, and 4) 5X106CFU anaerobic dose. Results indicate anaerobically cultured F2365 colonized the intestines consistently throughout the study unlike aerobic cultures. Additionally, intestinal damage was observed in challenged gerbils. Further goals include evaluating how viurlence is influenced in anaerobic conditions with varying bile concentrations and pH levels.