Relationship between thyroid autoantibodies and endemic goiter have been studied in 164 subjects from three different areas of endemic goiter: 91 patients and 31 healthy controls from Central Sardinia, 23 patients from Northern Latium, and 19 patients from Southern Latium. In subjects with endemic goiter from Sardinia higher levels of thyroid autoantibodies were present as compared to the healthy controls; microsomal fraction autoantibodies titer was higher than antithyroglobulin autoantibodies. In subjects from the two other endemic goiter areas the antimicrosomal and antithyroglobulin autoantibodies were absent, with the exception of one patient with basedow's goiter. It is suggested that some of the areas classified as positive for endemic goiter are indeed characterized by an extensive genetic predisposition to lymphocytic chronic thyroiditis complicated by nodular goiter.