Altered tPA expression may influence the fate of neurons after cerebral ischemia. We determined the changes in tPA and plasminogen activator inhibitor (PAI-1) expression in adult rat brain after transient middle cerebral artery (MCA) occlusion. Immunohistology revealed tPA staining in ipsilateral but not contralateral cortex and striatum 6 h after occlusion. This pattern was maintained at 24 h. Staining data was supported by Western blot data which showed no tPA protein in contralateral cortex at 3 h but abundant protein in ipsilateral cortex which increased further at 6 h and 24 h. In contrast there was prominent PAI-1 immunostaining and protein expression in control tissue after MCA occlusion but it diminished progressively at 3, 6 and 24 h in the lesioned cortex.