The relationships between hemodynamic state and plasma components of the renin-angiotensin and adrenergic nervous systems were studied in 42 patients admitted to an intensive care unit with acute heart failure. Patients were allocated to four subsets according to cardiac output and pulmonary wedge pressure. Plasma renin activity and angiotensin II were abnormally high in most patients with cardiac output less than or equal to 3.81 X min-1 and pulmonary wedge pressure greater than or equal to 18 mm Hg in contrast with values of patients of the 3 other subsets, which overlapped the normal range. On the other hand, plasma catecholamines were abnormally high in most patients. Angiotensin II was positively correlated with pulmonary wedge pressure, urea and catecholamines and negatively correlated with cardiac output and natremia. Norepinephrine was uncorrelated with hemodynamic parameters but epinephrine was negatively correlated with cardiac output. A discriminant linear function was calculated for prognosis of survival: cardiac output was the most important factor. The rise of angiotensin II and epinephrine were not unfavorable factors if their correlations with other factors (eg cardiac output and urea) were taken into account.