We determined functional and morphological changes of the heart by 2-dimensional and pulse Doppler echocardiography in 20 patients with primary aldosteronism and compared the results with those in 50 healthy normotensive subjects, 12 patients with Cushing's syndrome, 9 patients with pheochromocytoma, and 47 patients with essential hypertension. All hypertensive groups had greater left ventricular mass indexes than did the normotensive group (76.9 +/- 17.2 g/m2). Despite similar age distribution, blood pressure during antihypertensive treatment, and duration of hypertension, the primary aldosteronism group had a significantly greater left ventricular mass index (152.5 +/- 42.5 g/m2) than did the Cushing's syndrome (103.4 +/- 37.5 g/m2), pheochromocytoma (122.4 +/- 28.5 g/m2), and essential hypertension (101.4 +/- 32.8 g/m2) groups. The left ventricular posterior wall thickness and interventricular septal wall thickness were significantly greater in the hypertensive groups than in the normotensive group and also significantly greater in the primary aldosteronism group than in any of the other hypertensive groups. By contrast, there were no significant differences among the four hypertensive groups in any variable of systolic or diastolic function of the heart. The results suggest that left ventricular hypertrophy is more pronounced in patients with primary aldosteronism than in patients with other forms of hypertension. It is therefore important to echocardiographically evaluate cardiac hypertrophy as a risk factor of morbidity and mortality in patients with this low renin hypertension.