Oxidative stress has been implicated in the destruction of beta cells in type 1 diabetes (T1D). Thioredoxin has been shown to protect cells from oxidative stress and apoptosis. In this study, we screened for sequence variants of the human thioredoxin gene (TXN), and studied the association of the variants in persons with T1D in Japanese. The frequency of the A allele of the G/A SNP in the 3' flanking region was highest in T1D (8.4%), followed by type 2 diabetes (6.8%), and the lowest in the controls (5.9%), suggesting the contribution of TXN polymorphism to susceptibility to T1D.