In order to evaluate the potential relationship between atrial pressure development and release of atrial natriuretic factor (ANF), 33 patients with congestive heart failure were investigated with right-sided heart catheterization during supine graded bicycle exercise. Resting plasma ANF levels were higher in patients with heart failure as compared with normal controls, 75.1 +/- 45.6 pmol/l vs 12.3 +/- 6.2 pmol/l (mean +/- SD, N = 33 and N = 42, respectively) and correlated with right atrial, pulmonary arterial and pulmonary capillary wedge pressures. During exercise, central pressures rose steeply with a simultaneous increase in plasma ANF in all patients. Plasma ANF levels correlated with heart rate at a workload of 25 w, to pulmonary arterial and pulmonary capillary wedge pressure at 50 w, and to pulmonary capillary wedge pressure at 75 w. The increments in ANF levels between the different workloads during exercise did not correlate with the corresponding increments in pressure values. In congestive heart failure, the capability of ANF secretion in consequence to pressure stimuli is preserved, and left atrial pressure seems to be the major stimulus for ANF release during exercise.