Sixty-six cultures of food microorganisms were screened by spot-plate tests on their ability to influence the growth of four strains of Staphylococcus aureus, two enterotoxigenic and two not. The six test media were selected for differences in complexity and to simulate natural foods. The most consistently inhibitory cultures for S. aureus were: Streptococcus faecium, Streptococcus faecalis, S. faecalis var. liquefaciens, a nisin-producing Streptococcus lactis, and various meat lactobacilli. Other cultures were less consistently inhibitory, and many were not inhibitory or were even stimulatory. Growth of two enterotoxigenic strains of S. aureus in meat infusion broth at 15°, 30° and 44° C. was only moderately reduced by simultaneous growth of Escherichia coli strain Gratia, but was markedly reduced by growth of E. coli H52, especially at 15° C. and 44° C.