In patients with chronic heart failure (CHF), physical exertion frequently is associated with higher than normal ventilatory levels and dyspnea. To determine the prevalence of such excessive ventilatory responses in CHF and whether this excessive ventilation is a result of acute increases in intrapulmonary pressure during exercise, minute ventilation (VE) and pulmonary artery (PA) wedge pressure were measured during maximal bicycle exercise in 38 patients with chronic CHF. It was then determined whether reducing the PA wedge pressure during exercise with prazosin (9 patients) or dobutamine (6 patients) reduced ventilatory levels toward normal. To compare ventilation between patients, VE was correlated with minute carbon dioxide production (VCO2) (r greater than or equal to 0.90); the calculated VE at a VCO2 of 1 liter/min (VE-CO2) was derived from this relation and used as a normalized index of ventilation. During exercise, VE-CO2 ranged from 27 to 71 liters/min, exceeding the normal range in 37 of 38 patients (normal 33 liters/min or less). VE-CO2 did not correlate with peak exercise PA wedge pressure and correlated only weakly with PA wedge pressure at rest (r = 0.48). Acute reduction in the PA wedge pressure during exercise with prazosin or dobutamine did not significantly reduce VE-CO2. These data suggest that ventilatory levels are frequently excessive during exercise in patients with CHF and therefore may provide a useful, objective index of their altered pulmonary function. In addition, our data suggest that this excessive ventilation is not a result of acute changes in intrapulmonary pressure during exercise.