Immunocytochemical and quantitative studies on vascular reaction (angiogenesis) in cortical border zone of infarct were undertaken. Intensity and temporal profile of angiogenesis was assessed in 60 patients aged between 48 and 69 (younger group), and between 70 and 92 (older group), with cerebral infarct in the area of middle cerebral artery vascularization, who died during the first six weeks following the stroke. We have found that angiogenesis was a multistage process in which four stages were distinguished: phase of primary activation of endothelial cells, two consecutive phases of active angiogenesis and final phase of only sporadic proliferation of vessels. The distinction of phases in a multiphase angiogenic cascade helped us to evaluate the correlation with survival time and the age of patients. The most pronounced intensification of angiogenesis and increased density of CD 31 positive capillaries in penumbra were observed in the second phase, especially in younger patients. The duration of the penumbral neovascularization decreased in the older age patient. Our results indicate that sprouting angiogenesis is a quantitatively significant source of vessels in the cerebral infarct border zone. However, non-therapeutically stimulated angiogenesis developed only 3-4 days after the stroke, that is beyond the period of reversible changes in ischemic penumbra recognized as a "therapeutical window" in the human brain. The angiogenic therapy opens a new way towards the revascularization of ischemic brain infarct.