SUMMARY:The inhibitory effects ofPseudomonason selectedSalmonellaand poultry isolates were investigated. Two methods of demonstration of the inhibitory effects were used. A perpendicular streak technique was used as a preliminary screening procedure to determine relative degrees of inhibition exhibited by known strains ofPseudomonasagainst sensitive Salmonella and known organisms isolated from poultry. Spectropho‐ tometric analysis was also used to measure inhibitory activity produced by different concentrations of filtrates fromPseudomonas culturesagainst sensitive organisms.Inhibition of sensitive organisms was more pronounced with agar plates than with cell density methods which employed broth. The production of pigment appeared to be related to the ability of differentPseudomonascultures to produce inhibition. Concentration of sensitive cells did not appear to be a limiting factor, since inhibition was demonstrable at both high and low levels of inocula.Pseudomonasstrains were inhibitory to strains of Salmonella,Staphylococcus, Escherichia and Streptococcus.None of the inhibitory strains ofPseudomonasisolated from poultry were mutually repressive. However, one strain ofPseudomonas aeruginosanot isolated from poultry did cause inhibition of growth of all of thePseudomonasisolated from poultry. The public health significance of this work in relation to potential pathogens on processed poultry is discusse