The deposition of beta A4-amyloid in senile plaques in the brain and small cerebral vessels is one of the pathological hallmarks of Alzheimer's disease (AD). Serine protease inhibitors (serpins) such as alpha 1-antitrypsin and alpha 1-antichymotrypsin have been found to be associated with beta-amyloid deposits; interest in their role in the pathogenesis of AD has therefore recently increased. We have analyzed alpha 1-antitrypsin phenotypes in a sample of 29 Polish patients with probable Alzheimer's disease. We have found an increased frequency of the PI*M3 allele (0.1897) in patients in comparison with the general population control (0.0563).