The authors studied the responses of the main systems of sympathetic and hormonal regulation in valvular aortic stenosis, a special model of dissociation between arterial pressure and left ventricular function. The series comprised 14 patients with an average age of 70 +/- 9 years without diuretic therapy presenting with pure calcific aortic stenosis without other valvular or coronary disease. All were in sinus rhythm; 5 were taking an angiotensin converting enzyme inhibitor. Plasma concentrations of endothelin 1, atrial natriuretic factor (ANF), arginine vasopressin (AVP), catecholamines, plasma renin activity (PRA), angiotensin II and aldosterone were measured in resting, fasting patients, by blood samplings from a peripheral vein immediately before cardiac catheterisation. The results were compared with the severity of the aortic stenosis (aortic valve area greater or less than 0.7 cm2), the ratio of left ventricular work/myocardial mass (greater or less than 0.6) and treatment (with or without ACE inhibitors). Catecholamine levels were much higher in severe aortic stenosis (noradrenaline: 579 +/- 66 pg/ml when valve surface area > 0.7 cm2 versus 900 +/- 92 pg/ml when valve surface area < 0.7 cm2; p < 0.01). Endothelin -1 and AVP concentrations were normal. Whereas PRA was normal, aldosterone levels were increased in patients without treatment by ACE inhibitors. This treatment did not, however, normalise the noradrenaline levels. The increase in ANF concentration was large when left ventricular work decreased with respect to myocardial mass (190.8 +/- 42.3 pg/ml if W/M was decreased versus 82.7 +/- 15.4 pg/ml when W/M was normal): this could be related to the degree of left ventricular hypertrophy.