The oxidative effect of hydrogen peroxide, ascorbic acid and glucose in the presence of transition metals was studied. Incubation of bovine lens membranes with hydrogen peroxide/ metal, ascorbic acid/metal and glucose/metal systems resulted in a significant augmentation of thiobarbituric acid-reactive substance content in the membranes. Presence of α-tocopherol decreased the extent of oxidative damage. This oxidation was found to be mediated by hydroxyl radicals. Dependence of hydroxyl radical generation upon the buffer used has been observed. In all experiments Cu(II) ions exhibited a higher efficiency compared to Fe(II) ions.