We examined the association between HLA-DQ and refractory Behçet's disease at the genomic DNA level. Using a restriction endonuclease Taq I and a DQ beta cDNA probe, we identified the 1.9 kb DQ beta restriction endonuclease fragment tightly associated with refractory Behçet's disease. This observation indicates that genomic HLA-DQ variations affect the development of refractory Behçet's disease.