Twenty eight patients (25F, 3M) affected by autoimmune and non-autoimmune thyroid diseases were studied. HSP 70 antibodies were present in 21.4% of patients. Five of them were affected by Graves' disease and one by De Quervain's thyroiditis. The HSP 70 antibodies mean values of patients were significantly higher than the normals (p < 0.05). This datum was confirmed by Western blotting. The presence of HSP 70 antibodies in the sera of those patients may support the link between the protein and the thyroid autoimmune processes.