Interleukin-4 (IL4) is an anti-inflammatory cytokine that may play a role in the inflammation pathology observed surrounding senile plaques, and may also associate with Alzheimer's disease (AD) pathogenesis. Recently, it has been reported that a single nucleotide polymorphism in the IL4 gene promoter region, IL4 +33C/T polymorphism, associates with its phenotype. It was thought that the IL4 +33C/T polymorphism causing high IL4 production may reduce the risk for AD. In the present study, therefore, we investigated this mutation in 108 healthy controls and in 178 sporadic AD cases by the polymerase chain reaction restriction fragment length polymorphism method in a Japanese AD population. Allelic frequencies with +33C/T polymorphism in the gene were 35.6 and 32.6% in the control and AD groups, respectively. Our results failed to demonstrate an association between this polymorphism and Japanese sporadic AD. We also tested whether the IL4 functional variants were regulated by this polymorphism in a portion of the subjects (16 AD cases and 13 control cases). We could not find any relationship between the IL4 +33C/T polymorphism and plasma IL4 concentration.