Localization of a locus for atopy to chromosome 16p12–p11 and reported associations of Ile50Val and Gln551Arg polymorphisms in interleukin-4 receptor α chain (IL 4R gene) with atopy prompted us to sequence the gene in 27 adult atopic dermatitis (AD) and 29 non-atopic (non-AD) subjects. Among six known polymorphisms, Gln551Arg was significantly associated with AD (P = 0·01). This polymorphism was found to be heterozygous in six of 27 patients with AD but none of the 28 non-AD controls. Ile50Val, which was previously reported to be associated with atopic asthma in Japan, showed no association with AD in our group. Glu375Ala and Cys406Arg also showed no association with AD. The IL 4R gene should thus be considered a compelling candidate gene for AD.