The antioxidant and membranoprotective properties of trolox have been studied in vitro. It is established that trolox possesses antioxidant properties, inhibiting ascorbate-dependent lipid peroxidation of liver homogenates and Fe(2+)-induced lipid chemiluminescence of egg-yolk lipids. In addition, trolox exhibits a broad spectrum of antiradical activity and interacts with stable free 2,2-diphenyl-1-picrylhydrazyl radical so as to reduce the generation of luminol radicals and reactive oxygen species and to bind peroxy radicals. Trolox also possessed membranoprotective properties, being capable of reducing the oxidative hemolysis of erythrocytes.