The alpha1-antichymotrypsin and apolipoprotein-E polymorphisms were investigated in patients suffering from Alzheimer's syndrome and non-demented psychiatric inpatients as controls. The apolipoprotein E allele 4, well known as risk factor, tended to be elevated in the index group. The frequency of the alpha1-antichymotrypsin allele A was significantly increased in patients with Alzheimer's syndrome: 0.647 vs. 0.483 (chi-square test, p < 0.05). We conclude that, apart from the apolipoprotein E allele 4, the alpha1-antichymotrypsin allele A possibly represents a second genetic factor increasing individual's risk for Alzheimer's syndrome.