It is well known that light emission is related to lipid peroxidation in biological material, and that this process occurs spontaneously in the brain. tert-Butyl hydroperoxide (tBHP) is an organic peroxide widely used as initiator of free radical production in several biological systems. However, the prooxidant capacity of this compound remins unclear. To clarify its role in brain spontaneous autooxidation, rat brain homogenates were incubated with and without tBHP. Light emission and lipid peroxidation were measured by luminometry and the TBARs test, respectively. Several inhibitors of free radical-induced lipid peroxidation were also used. These inhibitors included ascorbate, EDTA, and desferrioxamine. Our results indicate that the pattern of light emission spontaneously produced in brain was different from that observed after the addition of tBHP to the homogenates, and that these differences depended on the tBHP concentration. The main difference was that tBHP caused a rapid light emission that reached its maximum more quickly than in the case of spontaneous emission. Addition of ascorbate resulted in an increase in chemiluminescence in presence of tBHP. In contrast, EDTA and desferrioxamine inhibited light emission in homogenates both with and without tBHP. The results of MDA determination were similar to those described, including the effect of inhibitors. A common feature in MDA and luminometric determinations was the dispersion of data. In conclusion, these results suggest that tBHP, under specific conditions, modify the kinetic pattern of brain spontaneous autooxidation.