The characteristics of lactic acid bacterial fermentation and the principal antimicrobial factors produced by lactic acid bacteria (LAB) are reviewed and assessed. The principal anti-microbial factor identified is the ability of all LAB to produce organic acids and decrease the pH of foods in which they grow. Other factors such as the production of bacteriocins, hydrogen peroxide and ethanol may all play a contributory role in assuring the safety of fermented foods but their contribution is secondary. The efect of fermentation on non-bacterial pathogens is discussed. A tabulation is made of results from a number of published studies of the effects of fermentation on the fate of different bacterial pathogens in a vareity of food materials.