The purpose of this study was to examine the ventilatory responses during a six-minute walk test (6MWT), an incremental shuttle walking test (ISWT), and a cycle ergometer test (CET) in patients with chronic obstructive pulmonary disease. Twelve subjects (11 male, age 72.2 years, with a forced expiratory volume in one second of 53.6% of the predicted normal) took part in the study. Throughout the three exercise tests, oxygen uptake (V'Ｏ₂), carbon dioxide production (V'CO₂), minute ventilation (V'E), and heart rate (HR) were measured using a portable breath-by-breath system. Oxygen saturation (SpO₂) and breathlessness were recorded at the end of each minute during the tests. There were no significant differences among the three exercise tests in terms of the peak values for V'O₂, V‘CO₂, V'E, HR, and breathlessness. SpO₂ was significantly lower in both walking tests (6MWT: 89.8 ± 3.3%, ISWT: 88.9 ± 3.8%) compared to values in the CET (93.3 ± 2.3%) (p < 0.05). V'O₂ during the 6MWT increased sharply for 2 minutes, and then showed a steady-state profile. During the CET and the ISWT, however, V'O₂ increased with respect to workload. In conclusion, the three tests clearly measure different aspects of exercise tolerance and should be considered complementary.