Lipid peroxidation has been associated with a number of specific manifestations related both to lens aging and cataract development. The assessment of the effect of various naturally occurring prooxidants as well as the development of antioxidant strategies has often been limited by the lack of appropriate and simple experimental models. In this study we discuss the adaptation of a method based on the incorporation of a fluorescent probe (parinaric acid) into biological membranes to monitor early stages of lipid peroxidation. After establishing the appropriate conditions, the method can be successfully applied to study peroxidation in bovine lens membranes, allowing for the evaluation of the effect of several free radical generating systems, including the following metal-dependent initiators: ascorbate/ iron, hydrogen peroxide/copper and cumene hydroperoxide/ copper. The inhibitory effect of the chelating agent diethylene-triaminepenta-acetic acid and the competitive hydroxyl radical scavenger sorbitol, was consistently observed on parinaric acid degradation, on hydroxyl radical yield and on the amount of thiobarbituric acid reactive material produced. It could be shown that oxidative degradation of the probe gives direct information on lens membrane susceptibility to a specific peroxidation system. Parinaric acid can therefore be used as an efficient oxidation probe to evaluate oxidative damage inflicted to lens membranes by different systems, allowing also the evaluation of the antioxidant effect of various drugs including those with potential anticataractogenic effect.