Type 1 diabetes is a heterogenous autoimmune disease and is frequently associated with other organ-specific autoimmune diseases, including autoimmune thyroid disease (AITD). Type 1 diabetic patients with AITD are known to have clinical and immunological features distinct from patients without AITD. This study investigated whether stromal cell-derived factor (SDF)-1 gene polymorphism is associated with susceptibility to type 1 diabetes and AITD. SDF-1 is a powerful chemokine that upregulates T-cell migration and activation, and the gene for SDF-1 is located near type 1 diabetes susceptibility locus IDDM10. The SDF1-3'A variant (801 G to A in the 3'-untranslated region) was determined by the PCR-RFLP technique in 54 type 1 diabetic patients with AITD, 75 type 1 diabetic patients without AITD, 137 nondiabetic patients with AITD, and 106 healthy subjects in a case-control study. No significant differences on the allele and genotype frequencies of the SDF1 gene polymorphism were found, not only in type 1 diabetic patients with AITD compared with normal controls but also between nondiabetic patients with AITD and healthy control subjects. These results suggest that the SDF1-3'A variant is not associated with genetic susceptibility to type 1 diabetic patients and AITD.