We explored the temporal and topographic relations between local cerebral blood flow and regional brain prostaglandin profile following prolonged or transient occlusion of the middle cerebral artery in cats. Each experimental group was subjected to a sham operation, prolonged ischemia, or recirculation. Local cerebral blood flow was measured by the hydrogen clearance method. Following in situ freezing, cortical samples were obtained from each gyrus for determination of prostaglandin (PG) F2 alpha, PGE2, 6-keto-PGF1 alpha, and thromboxane (TX) B2 concentrations by radioimmunoassay. During prolonged ischemia, the concentrations of PGF2 alpha and PGE2 within the middle cerebral artery territory were significantly increased. Immediately after recirculation, there was a prominent but transient increase in PGF2 alpha and PGE2 in gyri that had been exposed to moderate ischemia (perifocal area). By contrast, the increases in these prostaglandins were slow and less prominent in gyri that had been exposed to severe ischemia (the focal area). The concentration of 6-keto-PGF1 alpha did not change during prolonged ischemia but transiently increased following recirculation in both the focal and perifocal areas. The TXB2 concentration did not change in any experimental group. Our study revealed a homogeneous increase in the regional brain content of PGE2 or PGF2 alpha in spite of the heterogeneous reduction of local cerebral blood flow during prolonged ischemia. Following recirculation, the focal and perifocal areas exhibited different patterns of prostanoid content. No correlation was found between local cerebral blood flow and the regional concentration of any prostaglandin examined.