To observe the expression of amyloid beta precursor protein and amyloid beta protein in neurons of hippocampal CA1 region after brain ischemia in human.Neuronal damage was examined by using HE staining, and expression of APP and Abeta(1-40) was determined by immunohistochemistry in the hippocampal CA1 region of the brain specimens of 43 patients who died 2 h-6 h, 7 h-24 h, 25 h-48 h, 49 h-72 h, 73 h-96 h, 97 h-144 h, or 145 h-168 h after cerebral ischemia and in 2 specimens of patients who died of other diseases as control group.The expression of Abeta(1-40) was 25.07 +/- 2.79 in the specimens 2 h-6 h after cerebral ischemia, peaked 73 h-96 h after cerebral ischemia (33.22 +/- 2.67), then decreased till 145 h-168 h after cerebral ischemia, however, all higher than that in the control group (2.88 +/- 0.18, all P < 0.05). The expression of beta-APP was 33.30 +/- 0.42 2 h-6 h after cerebral ischemia, was 28.11 +/- 2.03 7 h-24 h after cerebral ischemia, increased to peak value (32.32 +/- 1.36) 73 h-96 h after cerebral ischemia, and then decreased to 28.48 +/- 2.01, all higher than that of the control group (25.90 +/- 1.55) with significant differences between those 2 h-6 h and 73 h-96 h after ischemia and that of the control group (both P < 0.01). The increase of beta-APP was positively correlated with the expression of Abeta(1-40) 24 h after ischemia.The expression of beta-APP and that of Abeta(1-40) are up-regulated after cerebral ischemia, thus aggravating cerebral ischemia.