Aims: The aim of this study was to investigate the influence of environmental and physiological factors on the susceptibility of Escherichia coli to the Curvularia haloperoxidase system. Methods and Results: The Curvularia haloperoxidase system is a novel enzyme system that produces reactive oxygen species which have an antimicrobial effect. Escherichia coli MG1655 was exposed to the Curvularia haloperoxidase system under different temperatures and NaCl concentrations and after exposure to different stress factors. Temperature clearly affected enzymatic activity with increasing antibacterial effect at increasing temperature. The presence of NaCl interfered with the enzyme system and in the presence of 1% NaCl, no antibacterial effect could be observed at pH 7. Cells grown at pH 8(.)0 were in one experiment more resistant than cells grown at pH 6(.)5, whereas cells grown in the presence of 2% NaCl were more susceptible to the Curvularia haloperoxidase system. Conclusions: Environmental and physiological factors can affect the antibacterial activity of the Curvularia haloperoxidase system. Significance and Impact of the Study: The study demonstrates a systematic approach in assessing the effect of environmental and physiological factors on microbial susceptibility to biocides. Such information is crucial for prediction of application as well as potential side-effects.