The widespread application of pulmonary rehabilitation in chronic obstructive pulmonary disease (COPD) should be preceded by demonstrable improvements in function attributable to the programs. This review updates that reported in 2001. To determine the impact of rehabilitation on health-related quality of life (QoL) and exercise capacity in patients with COPD. We identified additional RCTs from the Cochrane Airways Group Specialised Register. Searches were current as of July 2004. We selected RCTs of rehabilitation in patients with COPD in which quality of life (QoL) and/or functional (FEC) or maximal (MEC) exercise capacity were measured. Rehabilitation was defined as exercise training for at least four weeks with or without education and/or psychological support. Control groups received conventional community care without rehabilitation. We calculated weighted mean differences (WMD) using a random-effects model. We requested missing data from the authors of the primary study. We included the 23 randomized controlled trials (RCTs) in the 2001 Cochrane review. Eight additional RCTs (for a total of 31) met the inclusion criteria. We found statistically significant improvements for all the outcomes. In four important domains of QoL (Chronic Respiratory Questionnaire scores for Dyspnea, Fatigue, Emotional function and Mastery), the effect was larger than the minimal clinically important difference of 0.5 units (for example: Dyspnoea score: WMD 1.0 units; 95% confidence interval: 0.8 to 1.3 units; n = 12 trials). Statistically significant improvements were noted in two of the three domains of the St. Georges Respiratory Questionnaire. For FEC and MEC, the effect was small and slightly below the threshold of clinical significance for the six-minute walking distance (WMD: 48 meters; 95% CI: 32 to 65; n = 16 trials). Rehabilitation relieves dyspnea and fatigue, improves emotional function and enhances patients' sense of control over their condition. These improvements are moderately large and clinically significant. Rehabilitation forms an important component of the management of COPD.