A weak association between subacute (de Quervain's) thyroiditis and HLA-DRw8 (relative risk = 2.19, X2 = 3.86) was observed. However, the association was not statistically significant if p value was corrected. Since it was confirmed that the association of subacute thyroiditis with HLA-B35 was primary, and since this association was extremely strong, the two models (dominant and recessive) for the effect of an HLA-linked gene which has a major effect on the pathogenesis of subacute thyroiditis were tested by the method described by Thomson & Bodmer using the frequency of HLA-B35 in the patients. The data most fit to the recessive model for the HLA-linked major gene involved in subacute thyroiditis.