Susceptibility to Graves' disease (GD), which is determined by environmental and genetic factors, is conferred by genes in the human leukocyte antigen (HLA) and genes unlinked to HLA, including the CTLA-4 gene. We recently described the association of GD with the vitamin D receptor (VDR) exon 2 initiation codon (VDR-FOK:I) polymorphism. An association of some VDR genotypes with osteoporosis, primary hyperparathyroidism, and some autoimmune diseases, such as insulin-dependent diabetes mellitus and multiple sclerosis, has been reported. We investigated the distribution of VDR gene polymorphism in 180 Japanese patients with GD (48 males and 132 females) and 195 controls (67 males and 128 females). A VDR allelic polymorphism was assessed by BSM:I endonuclease restriction after specific PCR amplification. Genotypic polymorphism was clearly defined as BB (no restriction site on both alleles), bb (restriction site on both alleles), or Bb (heterozygous). The distribution of genotype frequencies differed between patients with GD and controls (chi(2) = 7.53; 2 degrees of freedom; P: = 0.023). The relative risk conferred by at least 1 B allele (BB or Bb) was 1.5. We also found an association between VDR-APA:I polymorphism and GD. No relation was detected between this polymorphism and the VDR-FOK:I polymorphism in the patients. The present results support the association of the VDR gene with GD in Japanese by showing that the VDR gene could be a non-HLA-linked gene predisposing an individual to GD. The role of the VDR gene polymorphism should be further studied in other populations, and the distribution of other polymorphisms, such as the polyadenylase polymorphism further down the VDR 3'-untranslated region, should be studied in terms of GD susceptibility.