Effects of low-level laser therapy (442 and 532 nm) and LED radiation (650 nm) on mitochondrial respiration in experimental endotoxic shock have been studied. A model of experimental endotoxic shock in rats was obtained by intraperitoneal injection of lipopolysaccharide B. It was found that low-level laser therapy and LED radiation dramatically affected the rate of mitochondrial respiration in third and fourth states both in LPS-treated animals and in control experiments. The maximal increase of the mitochondrial respiration rate (of about 40 %) in LPS-treated animals was observed when blue laser was applied at the dose of 6 J/cm(2). Measurements of inner mitochondrial membrane surface potential with fluorescence probe JC-1 in LPS-treated rats showed in approximately 10 % decrease of potential in LPS-treated animals compared to control.