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Objectives: Focal cerebral ischemia is responsible for alterations of vascular permeability, and the loss of microvascular integrity is a primary source of subsequent hemorrhages. We evaluated the influence of different durations of ischemia and reperfusion on infarction size and microvascular damage after focal cerebral ischemia in the mouse. Methods: C57BL/6 mice (n = 39) were subjected to focal cerebral ischemia (I) and reperfusion (R). Consecutive brain sections were analysed for infarction volumes (Nissl-staining) and for collagen type IV (immunohistochemistry and western blot). Results: Infarction size (percentage of the infarction volume versus ipsilateral hemisphere) increased with total time of ischemia and reperfusion: 19 ± 2% (I3R0), 30 ± 2% (I3R3), 36 ± 4% (I3R12), 41 ± 4% (I1R24), 45 ± 6% (I2R24) and 58 ± 2% (I3R24). The ischemic hemispheres showed a significant progressive reduction of collagen type IV positive vessels (ischemic versus non-ischemic contralateral area): 90 ± 3% (I3R0), 88 ± 1% (I3R3), 82 ± 3% (I3R12), 85 ± 3% (I1R24), 79 ± 3% (I2R24), 72 ± 2% (I3R24). Conclusions: Both prolonged ischemia and reperfusion lead to an increased infarction volume, as well as progressive microvascular damage. [ABSTRACT FROM AUTHOR]