Objective: To study the role of alpha 1-antichymotrypsin in the pathology and pathogenesis of Alzheimer disease. Data source: Using the key terms "alpha 1-antichymotrypsin, Alzheimer disease", and the subtitle of Alzheimer disease "etiology, pathology, physiopathology, therapy", we searched the MEDLINE database for the relevant articles about Alzheimer disease and alpha 1-antichymotrypsin on human in English published from January 1990 to May 2004. Meanwhile, using the key terms "alpha 1-antichymotrypsin, Alzheimer disease", we searched the Chinese journals full-text database in Chinese during the same period. Study selection: All articles were selected firstly, those were relevant to alpha 1-antichymotrypsin on the pathology and pathogenesis of Alzheimer disease were selected. Researches on biochemistry and gene of alpha 1-aritichymotrypsin were excluded. The rest full text was looked up, analyzed and summarized. Data extraction: A total of 159 English articles were collected, among which, 135 were studying articles and 45 met the inclusion criteria. Among 11 Chinese articles, 2 were included. Data synthesis: Alpha 1-antichymotrypsin expressed significantly in the brain tissue. Termed as "pathological chaperone", alpha 1-antichymotrypsin played a role in amyloid formation, which was one of the important factors in pathogenic mechanism of Alzheimer disease. Conclusion: Alpha 1-antichymotrypsin plays an important role in the pathology and pathogenesis of Alzheimer disease. Some therapeutic intervention may be provided based on the studies of alpha 1-antichymotrypsin of Alzheimer disease.