We studied the relationship between physiologic parameters in cardiopulmonary exercise testing (CPET) and prognosis in terms of survival time in patients with chronic obstructive pulmonary disease (COPD) in order to accurately assess the severity of the disease. From a group of 195 patients with COPD who had consecutively undergone CPET between July 1989 and October 1997, we enrolled 120 subjects (mean age 67.6 years, 104 males) with exertional dyspnoea into a cohort protocol. Of these subjects, 34 (28.3%) died during the 3-5-year follow-up period after CPET. By univariate analysis, the following factors were significantly associated with survival time: age, body mass index, %FVC, %FEV1, FEV1%, PaCO2 at rest, severity of exercise-induced hypoxemia evaluated by DeltaPaO2/DeltaVO2 (PaO2-slope), oxygen uptake, ventilation, tidal volume, PaCO2 and oxygen pulse at maximum exercise, as well as prescribing long-term oxygen therapy. By multivariate analysis, age and the PaO2-slope showed significance as independent prognostic factors, and the PaO2-slope was most closely associated with the survival time. These results reveal that CPET is a useful technique to accurately assess the relationship between the functional impairments and the prognosis of patients with COPD.