This study examines whether the grading of officially acknowledged respiratory disability reflects exercise disorders in patients with chronic respiratory diseases. In order to do this, we analyzed the cardiopulmonary exercise testing (CPET) data of 258 patients with chronic obstructive pulmonary disease (COPD), 125 with sequela of pulmonary tuberculosis (TB) and 52 with interstitial pneumonia between 1989 and 2002. The peak oxygen uptakes of grade 1 and 3 COPD patients were 12.4 +/- 3.8 and 14.9 +/- 4.3 ml/min/kg (mean +/- SD), respectively. The worse the grade, the lower was the peak oxygen uptake, the differences being significant in COPD patients. Despite this, the peak oxygen uptake range overlapped greatly between grade 1 and grade 3 COPD patients. Sixty percent of patients with TB and 46% of patients with IP whose peak oxygen uptakes were similar to those of grade 1 COPD patients failed to be acknowledged as grade 1. There were no significant differences between the peak oxygen uptake of grade 1 COPD patients and grade 1 TB patients, grade 3 TB patients, and grade 4 IP patients. Patients with TB and IP showed more severe ventilatory and gas exchange disorders than those with COPD. We concluded that the present system of acknowledgement of respiratory disability in Japan did not accurately reflect exercise disorders in patients with chronic respiratory diseases. As well as this, we argue that there is discrimination between patients with COPD, TB and IP. It is necessary to establish an alternative system, reflecting exercise disorders evaluated by CPET to offer a more accurate acknowledgement.