In the present work we have found in a relatively large series of thyroid cancer patients (n = 161) that both HLA class I (B35) and class II (DR11) antigens are susceptibility factors only in the papillary tumor group of patients, B35 association p value is found at the limit of significance (pc(120) = 0.05); the follicular group did not show any HLA association, suggesting that the etiopathogenesis of each type of cancer is different.