The purpose of this study is to determine whether the p53 protein, a product of the p53 tumor suppressor gene, that has been associated with the 72 kDa heat shock protein (hsp72), is expressed in ischemic brain. Adult Wistar rats (n = 5) were subjected to 120 minutes of middle cerebral artery occlusion. Twelve hours after reopening the artery, brain tissue was analyzed to determine the extent of neuronal damage (hematoxylin and eosin), and the distribution of p53 and hsp72 (monoclonal antibodies). Our data demonstrate that p53 is expressed in regions of neuronal necrosis; in contrast, morphologically intact neurons express hsp72. The data suggest that the presence of p53 is associated with cell death and that hsp72 may regulate p53 function.