In this article, we report on Some physiological aspects of the synthesis of extracellular L-lysine-α-oxidase (LO) by the fungus Trichoderma cf. aureoviride Rifai VKM F-4268D under salt stress conditions and discuss the possible role of this enzyme for the producer. It has been shown that The synthesis of extracellular LO and proteolytic enzymes is induced in the fungus T. cf. aureoviride Rifai VKM F-4268D during submerged cultivation on wheat bran under salt stress. It has been shown that LO biosynthesis is accompanied by H2O2 accumulation in the growth medium. It seems that the extracellular LO synthesis followed by hydrogen peroxide production under stress conditions provides an adaptive advantage for the producer fungus in its competition with other organisms. © 2012 Pleiades Publishing, Ltd.