An association between altered risk of Alzheimer's disease (AD) and the interleukin-1A (IL-1A) gene was recently reported in two independent studies. Here, the IL-1A polymorphism was analyzed in a third population of 247 AD patients and 187 control individuals. In support of the published findings, the IL-1A 2/2 genotype was associated with an increased risk of early onset AD (odds ratio of 3.1, P = 0.02). Clinically, the IL-1A 2/2 genotype was associated with an earlier age of onset, but not with a change in the rate of progression of AD.