Efforts to control harmful pathogens through the application of various chemicals with proven bactericidal properties have not been adequately effective.  Many of these chemicals also have the potential of adverse health impact through reactive effects from their residual presence on products.  This study was therefore undertaken to determine in vitro inhibition of E. coli O157:H7 growth by three GRAS (generally recognized as safe) chemicals (L-ascorbic acid, lactic acid, and propyl gallate).Since E. coli O157:H7 is one of the most hazardous pathogenic bacteria and has become a well known pathogen in food and dairy industries. Therefore, five strains of E. coli O157:H7 with populations of approximately 3.5 log CFU/ml were individually inoculated into tryptic soy broth (TSB) supplemented with either L-ascorbic acid, lactic acid, propyl gallate or a combination of these chemicals.  During an 8 h incubation period at 37ºC, microorganism growth (turbidity via optical density, OD) for each strain was determined at 2 h intervals using a spectrophotometer (610 nm).  At the end of incubation, TSB was also serially diluted (1:10) in sterile 0.1% peptone water and surface plated on tryptic soy agar.  The results show that concentrations required for L-ascorbic acid, lactic acid and propyl gallate to demonstrate the strongest inhibitory effect on the growth of the microorganisms were 1% (w/v), 0.3% (v/v), and 0.1% (w/v), respectively.  Combinations of 0.25% L-ascorbic acid or 0.025% propyl gallate with 0.2% lactic acid completely inhibited the growth of E. coli O157:H7 strains tested at an initial inoculum level.  There was no specific correlation of OD readings to cfus due to the increase of bacterial populations.  These results indicate that antioxidants used in this in vitro study may have the potential in controlling foodborne pathogens in vivo.