Phenol and its non-halogenated derivatives have been used for over 100 years as antiseptics to control growth of microorganisms. Their importance in controlling microbial growth in foods, however, has been recognized only recently. Phenolic compounds important in foods may be classed conveniently into three categories. First, there are those compounds currently approved for use in foods. This group includes methyl, propyl, and heptyl esters of p-hydroxybenzoic acid. Naturally occurring phenolic derivatives comprise the second category. Simple alkyl. hydroxy- and methoxy-phenol derivatives to complex polyphenols are included in this diverse group. The third type is food additives which are antimicrobials but are currently approved for other uses. The phenolic antioxidants are the only compounds in this category which have been tested thoroughly for their antimicrobial effectiveness. Each of these classes of phenolic compounds has widely varying inhibitory powers against certain bacteria, fungi and viruses. Their mode of action has been studied but has not been elucidated fully. A review of research on the spectrum of antimicrobial activity of these compounds as well as their proposed mechanism is presented.