CONTEXT: Animal studies have demonstrated that dietary sodium intake is a major influence in the pathogenesis of aldosterone-induced effects in the heart such as left ventricular (LV) hypertrophy and fibrosis. LV hypertrophy is an important predictor for cardiovascular morbidity and mortality. OBJECTIVE: We aimed to investigate the relationships between aldosterone and dietary salt and LV dimensions in patients with primary aldosteronism (PA). DESIGN AND PARTICIPANTS: This case-control study included 21 patients with confirmed PA and 21 control patients with essential hypertension matched for age, gender, duration of hypertension, and 24-h systolic and diastolic blood pressure. MAIN OUTCOME MEASURES: Patients were evaluated by echocardiography and 24-h urinary sodium (UNa) excretion while consuming their usual diets. RESULTS: Patients with PA had significantly greater mean LV end-diastolic diameter, interventricular septum and posterior wall thicknesses, LV mass (LVM) and LV mass index, and end systolic and diastolic volumes than control patients. UNa significantly positively correlated with interventricular septum, posterior wall thicknesses, and LVM in the patients with PA but not in control patients. In a multivariate analysis, UNa was an independent predictor for LV wall thickness and LV mass among the patients with PA but not in patients with essential hypertension. CONCLUSIONS: These findings emphasize the importance of dietary sodium in determining the degree of cardiac damage in those patients with PA, and we suggest that aldosterone excess may play a permissive role. In patients with PA, because a high-salt diet is associated with greater LVM, dietary salt restriction might reduce cardiovascular risk.