Studies have indicated variations in the degree of efficacy of certain commercial disinfectants used in poultry production facilities. We used an adequate method of in vitro testing to compare the efficacy of disinfectants while testing them in conditions similar to those of the poultry facilities. BioSentry 904, ethylenediaminetetracetic acid (EDTA)-Tris, and a combination of the two were tested by this method against five field isolates of Pseudomonas aeruginosa at 10³, 10⁶, and 10⁹ colony-forming units (CFU)/ml. At the 10⁹ CFU/ml concentration, most compounds failed to achieve a total kill with a contact time of 15 min. When tested at bacterial concentrations of 10³ CFU/ml, the combination of EDTA-Tris mixed at a 1:1 ratio with BioSentry 904 killed the bacteria upon initial contact (≤0.05 min). This disinfectant mixture exhibited antagonistic, indifferent, or synergetic effects when exposed to different bacterial isolates at a concentration of 10⁶ CFU/ml.