The relative ability of acetic, benzoic, citric, lactic, propionic, and sorbic acids to inhibit the growth of six common meat spoilage bacteria ( Brochothrix thermosphacta , Carnobacterium piscicola , Lactobacillus curvatus , Lactobacillus sake , Pseudomonas fiuorescens , and Serratia liquefaciens ) was compared under otherwise optimum conditions (BHI or MRS broths; 20°C). Because of their low solubility in the growth media, benzoic and sorbic acids could only be used in low concentrations (below 0.15% [wt/vol]) and did not efficiently inhibit bacterial growth. All other acids totally inhibited growth at concentrations ranging from 0.1 % to 1% (wt/vol). On a weight basis, acetic acid was found to be the most inhibitory, followed by propionic. lactic, and citric acid, while the order of efficiency was reversed (citric> lactic> propionic> acetic) when the acid concentrations were expressed on a molar basis or when the acid effectiveness was evaluated relative to the concentration of undissociated molecules. Overall, the lactobacilli were the bacteria most resistant to the action of organic acids, followed by P. fiuorescens and S. liquefaciens , while B. thermosphacta and C. piscicola were considerably more sensitive.