The clinical course of congestive heart failure (CHF) and mitral valve stenosis (MVS) is accompanied by episodes of dyspnea, wheezing, and cough, symptoms also observed in patients with bronchial hyperreactivity. However, it is still controversial whether bronchial hyperreactivity is demonstrable in patients with chronic overload of the pulmonary circulation. In order to examine the effects of CHF on the respiratory function, we performed pulmonary function tests, titrated bronchial acetylcholine provocations, and left and right heart catheterization in 21 patients with impaired left ventricular function (mean ejection fraction, 37 percent, NYHA class 3), 5 patients with MVS, and 17 control patients with coronary artery disease (mean ejection fraction, 63 percent). Bronchial hyperresponsiveness was defined as an obstructive response to increased doses of inhaled acetylcholine. A 20 percent fall in forced expiratory volume in the first second (FEV1), a 100 percent increase in total airway resistance (Rtot), and a 60 percent reduction of pulmonary conductance (SGtot) were considered positive. Patients with impaired left ventricular function showed significantly higher airway resistance, and lower airway conductance at the maximal tolerated acetylcholine dose compared with control patients. Patients with MVS had a significant lower airway conductance. The induced bronchial obstruction was completely reversible upon inhalation of a beta 2-mimetic. We conclude that chronic overload of the pulmonary circulation is accompanied by bronchial hyperreactivity that may augment the symptoms of dyspnea in patients with CHF and MVS.