To compare the prevalence of positive autoantibodies in patients with thyroid disorders and healthy subjects in an iodine-replete area of the Islamic Republic of Iran, we studied 930 women in a clinic-based study 698 patients (286 hypothyroid, 140 hyperthyroid, 272 with simple goitre) and 232 healthy women. Serum thyroxine (T4), triiodothyronine (T3), thyroid stimulating hormone, and anti-thyroid antibodies were measured. Positive autoantibodies were detected in 75.5% of patients with hypothyroidism, 73.6% of those with hyperthyroidism, 48.9% of those with simple goitre and 35.8% of the control group (P < 0.001). Autoimmunity may have a role in the genesis of common thyroid disorders.