Exercise tolerance in chronic obstructive pulmonary disease (COPD) patients has been shown to be related to airway limitation and dyspnoea, but little is known about the effects of an emotional status on physical performance. We examined 49 COPD patients with a wide spectrum of airway limitation severity and hypoxaemia. Exercise tolerance was evaluated using the Six-minute Walking Distance Test (6MWD), dyspnoea at rest and on exercise was measured using the visual analogue scale, and the emotional status was evaluated using the battery of psychological tests. The average 6MWD (mean+/-SD) was 355+/-112 m. In the majority of patients a fall in arterial blood oxygen saturation (Sa,O2) on exercise of >3% was found. The mean dyspnoea score of 21+/-19 at rest increased to 66+/-19 on exercise. All subjects demonstrated an increased level of anxiety. The majority also demonstrated elevated emotional tension, and half of the study group showed signs of depression. Step-wise multiple regression analysis with results of 6MWD as dependent and other studied variables as independent variables showed that exercise tolerance depended mainly on airway limitation. The forced expiratory volume in one second (FEV1) explained 24% of the variance. The forced vital capacity added a further 10%, and arterial blood carbon dioxide tension contributed 7%. The dyspnoea level on exercise added only 0.9%. All four variables explained 42% of the variance. There was no correlation between 6MWD and any of the variables characterizing the emotional status. We conclude that the emotional status of chronic obstructive pulmonary disease patients is characterized by an increased level of psychological tension, anxiety and depression, but these do not affect exercise tolerance as assessed by the six-minute walking distance test.