Regional distribution and age-related change of Mn-, Cu/Zn-superoxide dismutase (SOD) and constitutive type of nitric oxide synthase (NOS) activities in the brain were determined using stroke-prone spontaneously hypertensive rats (SHRSP). In the hippocampus (HIP), Mn- and Cu/Zn-SOD activities in SHRSP of 31-week-old were significantly lower than those of 15-week-old or normotensive rats (WKY). From Mn-SOD immunohistochemical staining of several subfields of the HIP, our results suggested that SHRSP hippocampal CA1 was more vulnerable to oxidative stress compared with WKY and other subfields. In the 31-week-old SHRSP cerebral cortex (CC), the activities of Mn-, Cu/Zn-SOD and NOS were significantly lower than those in WKY. At this age, most of the SHRSP developed cerebral injuries. These observations indicated that hypertensive vascular disease observed in the SHRSP CC resulted from the decreased antioxidant capacity that is closely associated with the development of stroke and, in turn, shortened life span.