This chapter talks about antimicrobial compounds that are divided into two classes: traditional and naturally occurring. Antimicrobials are classified as traditional when they (i) have been used for many years, (ii) are approved by many countries for inclusion as antimicrobials in foods, or (iii) are produced by synthetic processes. Next, the chapter discusses the factors affecting activity and traditional antimicrobials and ester derivatives of some weak organic acids. Many fatty acid esters exhibit antimicrobial activity in foods, with glycerol monolaurate being one of the most effective. Traditional antimicrobials and natural food antimicrobials are important tools for preserving food from microbiological spoilage and the growth of pathogens. Despite the extensive research already completed on the sources of antimicrobials, their spectra of activity, and the levels required for successful inhibition of foodborne bacteria and fungi, more research is still needed to better elucidate the mechanisms of antimicrobial activity of many of the chemicals discussed in the chapter. In addition to validating the activity and elucidating the mechanistic features of antimicrobials, they will have to be proven toxicologically safe. Demonstrating the efficacy of antimicrobial compounds in food products at concentrations that do not have adverse sensory effects, as well as controlling the cost of these interventions, are likely the greatest hurdles to their future application.