OBJECTIVETo analyze the relationship between the proto-oncogene c-fos change and neuronal degeneration in the hippocampus of the patients with Alzheimer's disease.METHODSThe post mortem human hippocampal tissues were divided into three groups, namely, the aged, the young and Alzheimer's disease (AD) groups. Each group consisted of 10 patients. The diagnosis of AD was made by clinical manifestation and argentatine (Bodían) staining. Patients of both the young and the aged groups had no neurological disorders. The proto-oncogene c-fos mRNA was investigated in the hippocampal neurons using the method of in situ hybridization.RESULTSThe optical density of stained area and the integral within proto-oncogene c-fos mRNA revealed a significant increase in the hippocampal neurons in cases of Alzheimer's disease as compared with the controls.CONCLUSIONSThe over-expression of the proto-oncogene c-fos might play a role in the pathological process of Alzheimer's disease. These changes might result from a suffering stage of the hippocampal neurons or from a compensatory mechanism in the surviving neurons which are not yet affected-by the pathological process.