In order to assess bronchial responsiveness in patients with congestive heart failure secondary to congenital heart disease, we performed a histamine inhalation test while monitoring transcutaneous oxygen tension and compared the respiratory threshold to histamine with that obtained in patients with bronchial asthma. The inhalation test was performed by doubling concentrations of histamine solution for 2 min at 1 min intervals. The respiratory threshold of histamine was defined as the minimal concentration causing a drop in transcutaneous oxygen tension greater than 10% from baseline. Six of 10 patients with congenital heart disease and all of 12 patients with bronchial asthma had bronchial hyper-responsiveness to histamine. The mean of histamine concentration was 2750 micrograms/mL and 937 micrograms/mL, respectively. During the histamine inhalation test, respiratory resistance gradually increased in congenital heart disease patients. This was measured by the linear slope of transcutaneous oxygen pressure (-1.08 +/- 0.75 mmHg/min), whereas in the bronchial asthma patients it rapidly decreased at the infection point (-4.19 +/- 1.86 mmHg/min). We conclude that children with congestive heart failure had bronchial hyper-responsiveness. We suggest bronchial hyper-responsiveness to inhaled histamine in congestive heart failure was caused by the gradual increased respiratory resistance, which was different from that of bronchial asthma.