Reperfusion of ischemic tissue is associated with the formation of hydroxyl radical (OH.). In this report, a novel mechanism for (OH.) generation from (1O2) is proposed based on the experimental evidence from the present study. A number of experiments were performed which conclusively demonstrated the formation of 1O2 from the reaction of lactic acid and hypohalite radical. Singlet oxygen attacks the unsaturated olefinic derivatives, which are also formed during reperfusion of ischemic tissue. The reaction between 1O2 and olefinic compounds produces hydroperoxides, which ultimately form OH. radical. The validity of the above mechanism of OH. radical formation is warranted from our experimental results.