We have examined the neuroprotective efficacy of the mitochondrial uncoupler 2,4-dinitrophenol (DNP) in animals receiving striatal injections of the neurotoxin quinolinic acid. Animals administered DNP either 1 h before or 3 h following QA infusion developed lesions that were 25% smaller than control animals. Animals treated with the DNP analogue 2,4,6-trinitrophenol, which does not possess uncoupling activity in intact mitochondria, showed no neuroprotection. These results indicate that DNP, and other compounds that diminish the mitochondrial membrane potential, might provide a novel approach to the treatment of acute neurological injury.