An imbalance between oxidants and antioxidants is considered to play a role in the pathogenesis of chronic obstructive pulmonary disease (COPD). There is considerable evidence that an increased oxidative burden occurs in the lungs of patients with this disorder, and this may be involved in many of the pathogenic processes, such as direct injury to lung cells, mucus hypersecretion, inactivation of antiproteases, and enhancing lung inflammation through activation of redox-sensitive transcription factors. COPD is now recognized to have multiple systemic consequences, such as weight loss and skeletal muscle dysfunction. Moreover, it is appreciated that oxidative stress extends beyond the lung and may, through similar oxidative stress mechanisms as those in the lung, contribute to several of the systemic manifestations in COPD.