Experimental findings suggest that catecholamines increase protein synthesis and play a role in cardiac hypertrophy. We hypothesize that elevated circulating plasma catecholamines in pheochromocytoma influence cardiac structural and functional remodeling. We compared 15 patients with surgically proven pheochromocytoma and 15 with untreated essential hypertension; we matched the patients for age, sex, body surface area, and blood pressure (BP) levels. Left ventricular hypertrophy (LVH) was identified by M-mode echocardiography in six patients with pheochromocytoma and in four with essential hypertension. Among both groups there were no differences in cardiac structure, no correlation between left ventricular mass and BP, no significant differences in mitral E-F slope, no correlation between either plasma norepinephrine or plasma epinephrine levels, and no differences in the left ventricular structural indices measured. In the pheochromocytoma group, left ventricular end systolic stress and end systolic diameter were significantly lower and left ventricular percent fractional shortening was higher. Plasma norepinephrine levels were higher in the pheochromocytoma group, but did not differ among patients of that group with and without LVH. We conclude that in both pheochromocytoma and essential hypertension, only a subset of patients develop evidence of LVH, and that in pheochromocytoma, the elevation of circulating plasma catecholamines is not necessarily associated with LVH. These results indicate that factors other than catecholamines and BP determine the development of LVH in pheochromocytoma.