There is evidence that catecholamines may promote the development of cardiac hypertrophy in hypertension. To test the hypothesis that adrenaline directly determines left ventricular mass, normotensive Wistar rats were made adrenaline-deficient by adrenalectomy and hypertensive by administration of glucocorticoid. Blood pressure, heart rate, and body weight of the adrenalectomised group were not significantly different from a glucocorticoid treated control group with intact adrenals. Heart weight was significantly lower in the adrenalectomised rats, but this difference disappeared when heart weight was adjusted for body weight. It appears therefore that the presence or absence of adrenaline does not significantly affect cardiac mass in the presence of hypertension in this animal model.