The activity of the free radical scavenger, superoxide dismutase, was studied in focal cerebral ischemia produced in Mongolian gerbils (Meriones unguiculatus) by occluding the right common and left external carotid arteries under halothane anesthesia. After recovery from anesthesia animals were classified according to their neurologic symptoms. Five animals exhibiting neurologic symptoms such as hemiparesis and rolling seizures were reanesthetized 120 min after vascular occlusion and their brains frozen in situ with liquid nitrogen. A series of 20-micron-thick coronal sections was cut in a cryostat; pictorial representations of tissue pH, ATP, and glucose were obtained using fluorescent and bioluminescent techniques. Using a highly sensitive bioluminescent technique, Cu,Zn-superoxide dismutase (Cu,Zn-SOD) and Mn-superoxide dismutase (Mn-SOD) activities were then measured in samples from both ischemic and nonischemic regions of the remaining tissue block. Cu,Zn-SOD and Mn-SOD activities were, respectively, 13.9 +/- 0.7 X 10(3) units/g and 5.4 +/- 0.3 X 10(3) units/g in the nonischemic tissue, and 13.2 +/- 0.6 X 10(3) units/g and 5.0 +/- 0.2 X 10(3) units/g within the ischemic tissue. Thus focal cerebral ischemia does not lead to a global decrease in SOD activity, as observed by others after heart and liver ischemia.