Graves' disease (GD) and Hashimoto's thyroiditis (HT) are both common autoimmune diseases of the thyroid gland (AITD). The IL-4 is involved in both humoral and cellular immunity. The aim of this study was to test whether the IL-4 gene could be used as a genetic marker to predict the development of AITD amongst the Chinese population of Taiwan. For this study, a normal control group of 105 healthy subjects and two experimental groups featuring individuals afflicted with either GD (104 patients) or HT (109 patients) were examined. Polymerase chain reaction (PCR) was used to analyze the variable number of tandem repeats (VNTRs) polymorphism for the IL-4 gene intron 3 and PCR-based restriction analysis using endonuclease BsmFI was undertaken for the same gene at the promoter -590 position. We found no significant difference in the frequencies of presence of genotype and allelic variants for the IL-4 gene at both the intron 3 and the promoter regions between the normal control group and each of the two patient groups. These findings suggest that the IL-4 gene polymorphisms that arise at either intron 3 or promoter -590 positions are not suitable genetic markers for AITD among Taiwanese Chinese.