P>Objective To investigate the changes of β-amyloid peptide (Aβ), β-amyloid precursor protein (APP) and the distributions of Aβ subtype in rat brain under the condition of chronic cerebral hypoperfusion. Methods Cerebral blood hypoperfusion rat model by bilateral common carotid artery permanent ligation was made. Immunohistochemical staining was performed to observe the distributions and expressions of APP, Aβ SUB>1-40/SUB> and Aβ SUB>1-42/SUB> The amyloidosis of the blood vessels was observed by Congo red staining. Radioimmunoassay and Western blotting were employed to test the levels of Aβ and APP in cortex and hippocampus. Results Immunohistochemical staining revealed that the both APP and Aβ/P> P>SUB>1-40/SUB> were increased in hippocampal CA1 district after 90d hypoperfusion (both P<0.05), APP, Aβ/P> P>SUB>1-40/SUB> and Aβ SUB>1-42/SUB> did so in cortex and hippocampal CA1 district after 180d hypoperfusion (Aβ/P> P>SUB>1-40/SUB> in cortex EM>P/EM><0.01, others EM>P/EM><0.05). Aβ SUB>1-40/SUB> distributed homogeneously, while Aβ SUB>1-42/SUB> was aggregated in cytoplasm. Cerebral amyloid an