Patients suffering from Chronic Obstructive Pulmonary Disease (COPD) are usually evaluated for cardio-respiratory capacity on a flat surface even though these patients generally encounter discomfort only when climbing stairs or ascending a slope. The purpose of this study was to describe the cardio-respiratory evaluation of these patients on climbing stairs. A staircase test was carried out and compared to the 6-min walking test. The maximum duration of ascent was 2 min, covering a maximum of four flights of stairs. The conditions of the staircase test and the instructions given to the patients regarding walking were designed to be consistent with the activities of daily life. We recorded the height reached and the distance covered; we also recorded dyspnoea, oxygen saturation (SpO2) and heart rate (HR); we estimated the maximal oxygen consumption (VO2max) and the physiological cost index (PCI) during each test. The statistical analysis of the results was surprising: it showed that there was no significant difference between the 6-min walking test and the stair climbing test on the following criteria: estimated VO2max, SpO2, and variation in heart rate between rest and effort (DeltaHR); it also showed that these two tests correlated well for dyspnoea (p<0.0001). It appears that the PCI of stair climbing is much higher than the PCI of walking on a level surface. These results may be explained partly by the anaerobic metabolic pathway used predominantly by patients with COPD in brief periods of exertion and partly by the muscular dysfunction which also accompanies brief exertion. The use of the PCI adds greater precision to the interpretation of the results of cardio-respiratory evaluation of COPD patients. The value of this index is proportional to the incapacity described by these patients. The staircase test is complementary to the 6-min walking test, making it possible to evaluate restriction of activity in COPD patients. Its implementation is simple and accessible.