Of 21 food flavoring compounds tested against 39–40 organisms, 10 were ineffective at 1,000 ppm or 10 mM either at pH 6 or 8 and by either surface plating or in broth. The 11 effective compounds were d- and l-carvone, diacetyl, ethyl vanillin, eugenol, maltol, menthol, phenylacetic acid, phenylacetal-dehyde, 2,3-pentanedione and vanillin; with diacetyl and eugenol being the most effective. All were more effective at pH 6 than at pH 8. With the exception of maltol and phenylacetic acid, each was generally more effective against fungi than bacteria with the lactic acid bacteria being the most resistant. At pH 5.5 and 5°C, diacetyl was inhibitory to Pseudomonas fluorescens and P. geniculata at < 10 ppm. The findings suggest that compounds used in acid foods, ostensibly as flavoring agents, may exert antimicrobial effects when considered in context with all parameters of growth.