<正> Free radicals in ischemic and reperfused rat brain were measured by electron spinresonance（ESR） spectrometer.The inhibitory effect of allopurinol on the free radical genera-tion in reperfused rat brain was observed.The experimental results revealed that the free radi-cal content of the brain in the ischemia group was markedly higher than that in the control group（P<0.01）

that in the reperfusion group was markedly higher than that in the ischemia group（P<0.01）and that in the allopurinol group was markedly lower than that in the reperfusiongroup（P<0.01）.These results suggest that free radicals increase.greatly after cerebralischemia-reperfusion and that allopurinol plays a certain inhibitory role in the free radical genera-tion in the reperfused rat brain.