Cytokines play a key role in the regulation of immune and inflammatory responses and therefore are potential candidate genes for autoimmune thyroid disease. Polymorphisms in cytokine genes may effect gene transcription, causing individual variations in cytokine production. Several investigators have linked the interleukin-4 (IL-4) gene and autoimmune disease. The present population-based study was to investigate the polymorphisms of IL-4 gene promoter (-589C/T) in GD patients compared with a control group and determine the association with GD in a Thai population. The subjects included 137 GD patients and 137 healthy control subjects with similar ethnic and geographic backgrounds. The IL-4 gene polymorphism at position -589 in the promoter was analyzed using the PCR-RFLP. The protective effect of the -589T allele as suggested by Hunt et al in a Caucasian population was not observed in the present study. The -589T allele frequencies were similar between patients and control subjects (69% vs 69.3%) suggesting that this polymorphism can not be used as a genetic marker for GD susceptibility in Thais.