We investigated the possibility that a polymorphism of alpha 1-antichymotrypsin modifies the risk for Alzheimer's disease (AD). Testing 147 AD patients and 74 controls, we did not find evidence of an association between alpha 1-antichymotrypsin polymorphism and AD and also failed to detect a modifying effect of this polymorphism in patients carrying at least one epsilon 4 allele of apolipoprotein E.