The study was performed to evaluate the prevalence of thyroid abnormalities detected by ultrasonography and, in particular, of multinodular nontoxic goiter in primary aldosteronism. We analyzed 80 consecutive of patients with primary hyperaldosteronism (40 with unilateral adenoma and 40 with idiopathic hyperaldosteronism) and 80 normotensive healthy controls, comparable for age, sex, iodine intake, and geographical area. Blood pressure, thyroid palpation, thyroid function, and ultrasonography were evaluated. The prevalence of ultrasonographic thyroid abnormalities was 60% in primary aldosteronism and 27% in controls (p<0.0001). There was a statistically significant difference in prevalence of these abnormalities in unilateral adenoma and idiopathic hyperaldosteronism with respect to controls (p<0.05 and p<0.0001, respectively). The prevalence of multinodular nontoxic goiter in idiopathic hyperaldosteronism was higher than in controls (p<0.001) and, in particular, in female patients. From these data it seems to be worth considering the existence of primary hyperaldosteronism in patients with multinodular goiter and hypertension.